CAM 701133

Microwave Tumor Ablation

Category:Surgery   Last Reviewed:December 2020
Department(s):Medical Affairs   Next Review:December 2021
Original Date:December 2012    

Description 
Microwave ablation (MWA) is a technique to destroy tumors and soft tissue using microwave energy to create thermal coagulation and localized tissue necrosis. MWA is used to treat tumors not amenable to resection and to treat patients ineligible for surgery due to age, comorbidities, or poor general health. MWA may be performed as an open procedure, laparoscopically, percutaneously, or thoracoscopically under image guidance (eg, ultrasound, computed tomography, magnetic resonance imaging) with sedation, or local or general anesthesia. This technique is also referred to as microwave coagulation therapy.

For individuals who have unresectable primary or metastatic breast cancer who receive MWA, the evidence includes case series and a systematic review of feasibility and pilot studies conducted prior to 2010. The evidence is insufficient to determine the effects of the technology on health outcomes.

For individuals who have an unresectable primary or metastatic hepatic tumor who receive MWA, the evidence includes randomized controlled trials (RCTs), comparative observational studies, case series, and systematic reviews comparing MWA to radiofrequency ablation (RFA) and to surgical resection. The relevant outcomes are overall survival (OS), disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The body of evidence indicates that MWA is an effective option in patients for whom resection is not an option. Although studies had methodological limitations, they consistently showed that that MWA and RFA had similar survival outcomes with up to five years of follow-up in patients with a single tumor <5 cm or up to three nodules <3 cm each. In meta-analyses of observational studies, patients receiving MWA had higher local recurrence rates and lower survival than those who received resection, but the patient populations were not limited to those who had unresectable tumors. MWA was associated with lower complications, intraoperative blood loss, and hospital length of stay. The evidence is sufficient to determine the effects of the technology on health outcomes.

For individuals who have an unresectable primary or metastatic lung tumor who receive MWA, the evidence includes one RCT, retrospective observational studies, and systematic reviews of these studies. The relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The body of evidence indicates that MWA is an effective option in patients for whom resection is not an option. In the RCT, direct comparison of MWA and RFA in patients with primary or metastatic lung cancer (mean tumor size 1.90 cm [± 0.89] at baseline) found similar mortality rates up to 12 months of follow-up. In the first of three systematic reviews that included 12 retrospective observational studies, local recurrence rates were similar for MWA and RFA at a range of 9 to 47 months of follow-up. In the second systematic review with a meta-analysis, there was lower OS with MWA compared to RFA but studies were not directly comparable due to clinical and methodological heterogeneity. However, the authors concluded that percutaneous RFA and MWA were both effective with a high safety profile. In the third systematic review using a network meta-analysis, the weighted average OS rates for MWA were 82.5%, 54.6%, 35.7% 29.6%, and 16.6% at 1, 2, 3, 4, and 5 years, respectively. Limitations of the body of evidence included a lack of controlled studies and heterogeneity across studies. The RCT did not report results by tumor size or the number of metastases. The observational studies included in the systematic reviews did not report sufficient information to assess the effectiveness or safety of MWA in subgroups based on the presence of multiple tumors or total tumor burden. Therefore, conclusions about the evidence sufficiency can only be made about patients with single tumors. For this population, the evidence is sufficient to determine the effects of the technology on health outcomes.

For individuals who have an unresectable primary or metastatic renal tumor who receive MWA, the evidence includes one RCT that compared MWA to partial nephrectomy and case series. The relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. In the RCT, overall local recurrence-free survival at 3 years was 91.3% for MWA and 96.0% for partial nephrectomy (p=0.54). This positive outcome should be replicated in additional RCTs. There are also no controlled studies comparing MWA to other ablation techniques in patients with renal tumors. The evidence is insufficient to determine the effects of the technology on health outcomes.

For individuals who have unresectable primary or metastatic solid tumors other than breast, hepatic, lung, or renal who receive MWA, the evidence includes case series. The evidence is insufficient to determine the effects of the technology on health outcomes.

Background 
MICROWAVE ABLATION
Microwave ablation (MWA) is a technique that uses microwave energy to induce an ultra-high speed, 915 MHz or 2.450 MHz (2.45 GHz), alternating electric field, which causes water molecule rotation and creates heat. This results in thermal coagulation and localized tissue necrosis. In MWA, a single microwave antenna or multiple antennas connected to a generator are inserted directly into the tumor or tissue to be ablated; energy from the antennas generates friction and heat. The local heat coagulates the tissue adjacent to the probe, resulting in a small, 2- to 3-cm elliptical area (53 cm) of tissue ablation. In tumors greater than 2 cm in diameter, 2 to 3 antennas may be used simultaneously to increase the targeted area of MWA and shorten operative time. Multiple antennas may also be used simultaneously to ablate multiple tumors. Tissue ablation occurs quickly, within 1 minute after a pulse of energy, and multiple pulses may be delivered within a treatment session, depending on tumor size. The cells killed by MWA are typically not removed but are gradually replaced by fibrosis and scar tissue. If there is local recurrence, it occurs at the margins. Treatment may be repeated as needed. MWA may be used for the following purposes: (1) to control local tumor growth and prevent recurrence; (2) to palliate symptoms; and (3) to extend survival duration.

MWA is similar to radiofrequency (RFA) and cryosurgical ablation. However, MWA has potential advantages over RFA and cryosurgical ablation. In MWA, the heating process is active, which produces higher temperatures than the passive heating of RFA and should allow for more complete thermal ablation in less time. The higher temperatures reached with MWA (>100C) can overcome the "heat sink" effect in which tissue cooling occurs from nearby blood flow in large vessels, potentially resulting in incomplete tumor ablation. MWA does not rely on the conduction of electricity for heating and, therefore, does not flow electrical current through patients and does not require grounding pads, because there is no risk of skin burns. Additionally, MWA does not produce electric noise, which allows ultrasound guidance during the procedure without interference, unlike RFA. Finally, MWA can take less time than RFA, because multiple antennas can be used simultaneously.

Adverse Events
Complications from MWA are usually mild and may include pain and fever. Other complications associated with MWA include those caused by heat damage to normal tissue adjacent to the tumor (eg, intestinal damage during MWA of the kidney or liver), structural damage along the probe track (eg, pneumothorax as a consequence of procedures on the lung), liver enzyme elevation, liver abscess, ascites, pleural effusion, diaphragm injury, or secondary tumors if cells seed during probe removal. MWA should be avoided in pregnant women because potential risks to the patient and/or fetus have not been established, and in patients with implanted electronic devices (eg, implantable pacemakers) that may be adversely affected by microwave power output.

Applications
MWA was first used percutaneously in 1986 as an adjunct to liver biopsy. Since then, MWA has been used to ablate tumors and tissue to treat many conditions including hepatocellular carcinoma, breast cancer, colorectal cancer metastatic to the liver, renal cell carcinoma, renal hamartoma, adrenal malignant carcinoma, non-small-cell lung cancer, intrahepatic primary cholangiocarcinoma, secondary splenomegaly and hypersplenism, abdominal tumors, and other tumors not amenable to resection. Well-established local or systemic treatment alternatives are available for each of these malignancies. The potential advantages of MWA for these cancers include improved local control and other advantages common to any minimally invasive procedure (eg, preserving normal organ tissue, decreasing morbidity, shortening length of hospitalization). MWA also has been investigated as a treatment for unresectable hepatic tumors, as both primary and palliative treatment, and as a bridge to liver transplant. In the latter setting, MWA is being assessed to determine whether it can reduce the incidence of tumor progression while awaiting transplantation and thus maintain a patient’s candidacy while awaiting liver transplant.

Regulatory Status
Multiple devices have been cleared for marketing by the U.S. Food and Drug Administration (FDA) through the 510(k) process for MWA. The indications for use are labeled for soft tissue ablation, including partial or complete ablation of nonresectable liver tumors. Some devices are cleared for use in open surgical, percutaneous ablation or laparoscopic procedures. Table 1 is a summary of selected MWA devices cleared by the FDA.

The FDA used determinations of substantial equivalence to existing radiofrequency and MWA devices to clear these devices. FDA product code: NEY.

This evidence review does not address MWA for the treatment of splenomegaly, ulcers, or for cardiac applications or as a surgical coagulation tool.

Table 1. Selected Microwave Ablation Devices Cleared by FDA

Device

Indication

Manufacturer

Date Cleared

 

510(k) No.

 

VivaWave Microwave Ablation System

Coagulation of soft tissue

Probe modification

Vivant Medical, Inc.

ValleyLab

6/2002

 4/2006

K011676

K053535

Microsoulis Tissue Ablation System

Intraoperative coagulation of soft tissue

Microsoulis Americas, Inc

1/2006

K052919

MicroSurgeon Microwave Soft Tissue Ablation MTAD-100

MTD-200

Surgical ablation of soft tissue

Probe/design modifcations

MicroSurgeon, Inc.

8/2007

2/2009

K070023

 K082565

MedWaves Microwave Coagulation/Ablation System

General surgery use in open procedures for the coagulation and ablation of soft tissues

MedWaves Incorporated

12/2007

K070356

Acculis Accu2i pMTA Microwave Tissue Ablation Applicator

Acculis Accu2i pMTA Applicator and SulisV pMTA Generator

Intraoperative coagulation of soft tissue

Software addition

Microsoulis Holdings, Ltd

8/2010 

11/2012

K094021 

K122762

MicroThermX Microwave Ablation System

Coagulation (ablation) of soft tissue. May be used in open surgical as well as percutaneous ablation procedures.

BSD Medical Corporation

8/2010

K100786

EmprintTM Ablation System

EmprintTM Ablation System

Emprint™ SX Ablation Platform with Thermosphere™ Technology

percutaneous, laparoscopic, and intraoperative coagulation (ablation) of soft tissue, including partial or complete ablation of non-resectable liver tumors.

Same with design modification of device antenna for percutaneous use

3-D navigation feature assists in the placement of antenna using real-time image guidance during intraoperative and laparoscopic ablation procedures.

Covidien LLC

4/2014

12/2016

9/2017

K133821

K163105 

K171358

Certus 140 2.45 GHz Ablation System and Accessories

Certus 140 2.45 GHz Ablation System and Accessories

CertuSurgGT Surgical Tool

Certus 140™ 2.45 GHz Ablation System and Accessories

Certus 140 2.45GHz Ablation System

Ablation (coagulation) of soft tissue.

Ablation (coagulation) of soft tissue in percutaneous, open surgical and in conjunction with laparoscopic surgical settings.

Surgical coagulation (including Planar Coagulation) in open surgical settings.

Same indication with probe redesign

Ablation (coagulation) of soft tissue in percutaneous, open surgical and in conjunction with laparoscopic surgical settings, including the partial or complete ablation of non-resectable liver tumors.

NeuWave Medical, Inc.

10/2010

01/2012

7/2013 

 5/2016 

10/2018

K100744

K1132376

NEUWAVE Flex Microwave Ablation System (FLEX)

Ablation (coagulation) of soft tissue.

Design evolution of Certus 140 2.45GHz Ablation System (K160936)

NeuWave Medical, Inc.

3/2017

K163118

Solero Microwave Tissue Ablation (MTA) System and Accessories

Ablation of soft tissue during open procedures

Angiodynamics, Inc.

5/2017

K162449

Microwave Ablation System

Coagulation (ablation) of soft tissue

Surgnova Healthcare Technologies (Zhejiang) Co., Ltd

7/2019

K183153

FDA: Food and Drug Administration. 

Related Policies
70175 Cryosurgical Ablation of Primary or Metastatic Liver Tumors
70191 Radiofrequency Ablation of Primary or Metastatic Liver Tumors
70192 Cryosurgical Ablation of Miscellaneous Solid Tumors Other Than Liver, Prostate, or Dermatologic Tumors
70195 Radiofrequency Ablation of Miscellaneous Solid Tumors Excluding Liver Tumors
80111 Transcatheter Arterial Chemoembolization (TACE) to Treat Primary or Metastatic Liver Malignancies
80143 Radioembolization for Primary and Metastatic Tumors of the Liver

Policy
Microwave ablation of primary or metastatic hepatic tumors may be considered MEDICALLY NECESSARY under the following conditions:

  • The tumor is unresectable due to location of lesion[s] and/or comorbid conditions
  • A single tumor of ≤5 cm or up to 3 nodules <3 cm each

Microwave ablation of primary or metastatic lung tumors may be considered MEDICALLY NECESSARY  under the following conditions:

  • The tumor is unresectable due to location of lesion and/or comorbid conditions
  • A single tumor of ≤3 cm

Microwave ablation of more than a single primary or metastatic tumor in the lung is considered investigational/unproven and therefore NOT MEDICALLY NECESSARY.

Microwave ablation of primary or metastatic tumors other than liver or lung is considered investigational/unproven and therefore NOT MEDICALLY NECESSARY. 

Policy Guidelines 
Coding

Please see the Codes table for details.

Benefit Application
BlueCard/National Account Issues
State or federal mandates (e.g., FEP) may dictate that all U.S. Food and Drug Administration (FDA)-approved devices, drugs, or biologics may not be considered investigational, and thus use of these devices may be assessed only on the basis of their medical necessity.

Rationale
The evidence review was created in December 2011 and has been updated regularly with searches of the PubMed database. The most recent literature update was performed through September 28, 2020.

Evidence reviews assess the clinical evidence to determine whether the use of technology improves the net health outcome. Broadly defined, health outcomes are the length of life, quality of life (QOL), and ability to function, including benefits and harms. Every clinical condition has specific outcomes that are important to patients and to managing the course of that condition. Validated outcome measures are necessary to ascertain whether a condition improves or worsens; and whether the magnitude of that change is clinically significant. The net health outcome is a balance of benefits and harms.

To assess whether the evidence is sufficient to draw conclusions about the net health outcome of a technology, 2 domains are examined: the relevance and the quality and credibility. To be relevant, studies must represent 1 or more intended clinical uses of the technology in the intended population and compare an effective and appropriate alternative at a comparable intensity. For some conditions, the alternative will be supportive care or surveillance. The quality and credibility of the evidence depend on study design and conduct, minimizing bias and confounding that can generate incorrect findings. The randomized controlled trial (RCT) is preferred to assess efficacy; however, in some circumstances, nonrandomized studies may be adequate. RCTs are rarely large enough or long enough to capture less common adverse events and long-term effects. Other types of studies can be used for these purposes and to assess generalizability to broader clinical populations and settings of clinical practice.

Clinical Context and Therapy Purpose
The purpose of microwave ablation (MWA) in patients who have unresectable primary or metastatic solid organ tumors is to provide a treatment option that is an alternative to or an improvement on existing therapies.

The question addressed in this evidence review is: Does the use of MWA improve the net health outcome in individuals with unresectable solid organprimary or metastatic tumors?

The following PICO was used to select literature to inform this review.

Patients
The relevant populations of interest are those with unresectable primary or metastatic breast tumors,those with unresectable primary or metastatic hepatic tumors, those with unresectable primary or metastatic lung tumors, those with unresectable primary or metastatic renal tumors, and those with unresectable primary or metastatic solid tumors other than breast, hepatic, lung, or renal.

Interventions
The therapy being considered is MWA.

Typically, MWA is performed under conscious sedation in an outpatient setting.

Comparators
The following therapies are currently being used to manage unresectable primary or metastatic solid tumors: radiofrequency ablation (RFA), transcatheter arterial chemoembolization (TACE), and cryoablation.

Outcomes
The general outcomes of interest are overall survival (OS), disease-specific survival, symptoms, QOL, and treatment-related mortality and morbidity.

Treatment-related morbidities may vary by tumor type. For example, treatment for lung cancer may lead to pneumothorax. Follow-up for treatment-related morbidity is months postprocedure. Follow-up to monitor for OS and recurrence rates may be measured in years of follow-up.

Study Selection Criteria
Methodologically credible studies were selected using the following principles:  

  • To assess efficacy outcomes, comparative controlled prospective trials were sought, with a preference for RCTs and systematic reviews of these studies
  • In the absence of such trials, comparative observational studies were sought, with a preference for prospective studies.
  • To assess long-term outcomes and adverse events, single-arm studies that capture longer periods of follow-up and/or larger populations were sought.
  • Studies with duplicative or overlapping populations were excluded.

Unresectable Primary or Metastatic Breast Tumors
Review of Evidence
Systematic Reviews
A systematic review by Zhao and Wu (2010) assessing ablation techniques for breast cancer found that only 0% to 8% of breast cancer tumors were completely ablated with MWA.1 The studies identified by reviewers were mostly feasibility and pilot studies conducted in research settings.

Case Series
Zhou et al (2012) reported on 41 patients treated with MWA directly followed by mastectomy for single breast tumors with a mean volume of 5.26 cm (range, 0.09 to 14.14 cm).2 Complete tumor ablation was found by microscopic evaluation in 37 (90%) of the 41 tumors ablated (95% confidence interval [CI], 76.9% to 97.3%). Reversible thermal injuries to the skin and pectoralis major muscle occurred in 3 patients.

Section Summary
For individuals who have unresectable primary or metastatic breast cancer who receive MWA, the evidence includes case series and a systematic review of feasibility and pilot studies conducted prior to 2010. Relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The evidence is insufficient to determine the effects of the technology on health outcomes.

Unresectable Primary or Metastatic Hepatic Tumors
Review of Evidence
Systematic Reviews
Several systematic reviews have evaluated MWA for patients with liver tumors.3-7 The 3 most recent, published in 2016,3 2019,6 and 2020,7 are summarized in Tables 2 through 4. One of these reviews compared MWA to RFA,3,, 1 compared MWA to resection, 6,and 1 compared MWA to a variety of therapies, including RFA and resection.7,

Table 2. MWA for Hepatic Tumors: Comparison of Trials/Studies Included in SR & MA 

Study Chinnaratha et al (2016)3 Glassberg et al (2019)6 Cui et al 20207
Seki et al (1999)8    
Shibata et al (2002)9  
Xu et al (2004)10    
Lu et al (2005)11  
Tanaka et al (2006)12    
Wang et al (2008)13    
Ohmoto et al (2009)14  
Yin et al (2009)15    
Kuang et al (2011)16    
Imura et al (2012)17    
Qian et al (2012)18    
Chinnaratha et al (2013)19    
Ding et al (2013)20  
Stattner et al (2013)21    
Takami et al (2013)22    
Zhang et al (2013)23  
Abdelaziz et al (2014)24    
Shi et al (2014)25  
Tan et al (2014)26    
Zhang et al (2014)27    
Abdelaziz et al (2015)28    
Vogl et al (2015)29    
Xu et al (2015)30    
Potretzke et al (2016)31    
Zhang et al (2016)32  
Li et al (2017)33    
Philips et al (2017)34    
Ryu et al (2017)35    
Song et al (2017)36    
Xu et al (2017)37    
Yu et al (2017)38    
Zhang et al (2017)39    
Chen et al (2018)40    
Chong et al (2018)41    

MWA: microwave ablation; MA: meta-analysis; SR: systematic reviews;

Table 3. MWA for Hepatic Tumors: SR and MA Characteristics 

Study Dates Trials Participants Comparison N (Range) Design Duration
Chinnaratha et al (2016)3 1980-2014 10 Adults with either very early stage, early-stage (single tumor or up to 3 nodules with each measuring ≤3 cm) or multifocal/large HCC outside Milan criteria MWA vs RFA 1066 (42-198) 1 RCT, 9 observational ( 1 prospective, 8 retrospective) 5-45 months
Glassberg et al (2019)6 2006-2018 16 Adult patients with confirmed HCC or liver cancer MWA vs Resection 965 MWA; 755 resections (22-424) 1 RCT, 15 observational (2 prospective, 13 retrospective) 15 months-5 years
Cui et al (2020)7 1994-2017 15 Adults with HCC without extrahepatic malignant manifestations, vascular invasions, or contraindications for MWA MWA vs RFA
MWA vs Resection
2458 (53-460) 4 RCT, 11 nonrandomized clinical trials 15-53 months

MWA: microwave ablation; MA: meta-analysis; SR: systematic reviews; RFA: radiofrequency ablation; HCC: hepatocellular carcinoma; RCT: randomized controlled trial.

Table 4. MWA for Hepatic Tumors: SR and MA Results

Study Local Tumor Recurrence/Progression Overall Survival Disease-free Survival Adverse events
Chinnaratha et al (2016)3 MWA vs RFA MWA vs RFA   MWA vs RFA
Total N 1298 538 NR Major Complications
1043
Pooled odds ratio (95% CI), p 1.01 (0.67 to 1.50); p=0.98 1 year: 1.18 (0.46–3.03), p=0.73

3 year: 0.76 (0.44–1.32), p=0.33
NR 0.63 (0.29–1.38), p=0.25
I2, p I2=23%, p=0.23 1 year: I2=32%, p=0.2
3 year: I2=53%, p=0.09
NR I2=0%, p=0.8
Glassberg et al (2019)6 MWA vs resection
MWA vs resection


MWA vs resection


MWA vs resection
Risk ratio (95% CI), p 2.49 (1.19–5.22), p=0.016 1 year: 1.01 (0.99–1.03), p=0.409
3 year: 0.94 (0.88–0.99), p=0.03
5 year: 0.88 (0.80–0.97), p=0.01
1 year: 0.95 (0.90–1.01), p=0.085
3 years: 0.78 (0.65–0.94), p=0.009
5 years: 0.83 (0.58–1.17), p=0.284
Overall complications
0.31 (0.19–0.51), p<0.001
Major complications
0.24 (0.10–0.61), p=0.002
Cui et al (2020) MWA vs RFA MWA vs RFA MWA vs RFA MWA vs RFA
Pooled odds ratio (95% CI), p Local tumor progression at 1 year
1.28 (0.52–3.18) p=0.59
Progression-free survival at 3 years
1.05 (0.77–1.43), p=0.74
3 year: 0.94 (0.66–1.34), p=0.74
5 year: 0.83 (0.58–1.18), p=0.29
NR Major complications
1.04 (0.56–1.93) p=0.90
I2, p Local tumor progression at 1 year
I2=8%, p=0.34
Progression-free survival at 3 years
I2=35%, p=0.19
3 year: I2=40%, p=0.12
5 year: I2=23%, p=0.27
NR Major complications
I2=0%, p=0.47
  MWA vs resection MWA vs resection MWA vs resection MWA vs resection
Pooled odds ratio (95% CI), p NR 3 year: 0.89 (0.59–1.35), p=0.59 NR NR
I2, p NR 3 year: I2=0%, p=0.91 NR NR

MWA: microwave ablation; MA: meta-analysis; SR: systematic reviews; RFA: radiofrequency ablation; CI: confidence interval; N: sample size; NR: not reported.

Chinnaratha et al (2016) published a systematic review of RCTs and observational studies that compared the effectiveness and safety of RFA with MWA in patients who had primary hepatocellular carcinoma (HCC).3 PubMed, EMBASE, and Cochrane Central databases were searched between 1980 and 2014 for human studies comparing the 2 technologies. The primary outcome was the risk of local tumor progression ; secondary outcomes were complete ablation, OS, and major adverse events. Odds ratios were combined across studies using a random-effects model. Ten studies ( 1 RCT9, 1 prospective cohort, 8 retrospective) were included. One study was conducted in Australia and the others in China or Japan. Using the modified Newcastle-Ottawa quality assessment scale, the reviewers rated 5 of 10 studies high quality. The overall local tumor progression rate was 14% (176/1298). There was no difference in local tumor progression rates between RFA and MWA (odds ratio, 1.01; 95% CI, 0.67 to 1.50; p=0.98). The complete ablation rate, 1- and 3- year OS, and major adverse events were similar between the 2 modalities (p>0.05 for all). Subgroup analysis showed local tumor progression rates were lower with MWA for treatment of larger tumors (odds ratio, 1.88; 95% CI, 1.10 to 3.23; p=0.02). No significant publication bias was detected nor was interstudy heterogeneity (I2<50%, p>0.1) observed for any measured outcomes. The reviewers concluded that MWA and RFA are equally effective and safe.

Glassberg et al (2019) conducted a systematic review of MWA compared to resection in patients with HCC or metastatic liver cancer. One RCT (Xu et al [2015] 30) was included; the other studies (n=15) were observational (2 prospective, 13 retrospective). Patients who received MWA had a significantly higher risk of local tumor progression compared to those who received resection (relative risk , 3.04; p<0.001). At 1 year, OS did not differ between MWA and resection but 3- and 5-year OS was significantly higher in patients who had received resection. Overall and major complications were lower with MWA compared to resection. Additionally, operative time, intraoperative blood loss, and hospital length of stay were significantly lower with MWA. Some studies included patients that were nonresectable in the MWA treatment arm, but due to limited reporting and patient preference affecting which treatment was performed, the reviewers were not able to calculate the number of patients who were nonresectable or to conduct subgroup analyses by resectable versus unresectable tumors. Microwave ablation was typically selected for patients with smaller and/or deeper tumors, more comorbidities, and a preference for a less invasive procedure. The reviewers concluded that MWA can be an effective and safe alternative to hepatic resection in patients or tumors that are not amenable to resection, but more studies are needed to determine the target population that would benefit most from MWA.

Cui et al (2020) conducted a systematic review and meta-analysis of MWA compared to various treatment modalities. The analysis included 4 RCTs, with 3 comparing MWA to RFA38,9,24 and 1 comparing MWA to TACE.28 The remaining 11 studies were nonrandomized trials comparing MWA to RFA (n=8 studies), resection (n=2 studies), or ethanol ablation (n=1 study). Meta-analyses were not performed for MWA versus TACE or ethanol ablation, because these comparisons were only examined in 1 study each. Meta-analyses of studies comparing MWA to RFA found no difference in 3-year OS, 5-year OS, local tumor progression at 1 year, progression-free survival at 3 years, or major complications. A meta-analysis of 2 nonrandomized studies comparing MWA to resection found no difference in 3-year OS between treatments; however, this comparison is limited by the small number of studies included and the lack of RCTs included. The reviewers concluded that MWA showed similar safety and efficacy compared with RFA, but higher quality clinical studies are needed to validate the superiority of MWA.

Randomized Controlled Trials
Five RCTs have compared MWA to RFA in patients with primary hepatic tumors42,9,38,24,43, and 1 RCT has compared MWA to resection30; the majority of these trials were included in the systematic reviews and meta-analyses described above and are not discussed in further detail here. Tables 5 through 8 summarize the characteristics, results and relevance and design and conduct limitations of trials that have not been included in systematic reviews or meta-analyses.

An RCT by Vietti Violi et al (2018) compared the effectiveness of RFA and MWA in treating inoperable HCC in 152 patients with up to 3 lesions of 4 cm or smaller.42 At 2 years, 6% (6/98) of lesions treated with MWA had local tumor progression versus 12% (12/104) of lesions treated with RFA (relative risk, 1.62; 95% CI , 0.66 to 3.94; p=0.27). Few complications and no treatment-related deaths were reported for either group. OS at 2 years was not significantly different between the groups. Because some patients did not receive the allocated treatment or were lost to follow-up, the analyses were per-protocol rather than intention-to-treat. In addition, the investigators had planned to assess the effects of the treatments on larger lesions, but only a few patients had lesions of nearly 4 cm, making a detailed analysis impossible. A 5-year follow-up is planned for this study.

Chong et al (2020) conducted an RCT comparing MWA to RFA in 93 patients with HCC (up to 3 lesions of 5 cm or smaller).43 Mean tumor size was 3.1 cm in the MWA group and 2.8 cm in the RFA group. The primary outcome of this study was the rate of complete ablation at 1 month, which did not differ significantly for MWA (95.7%) versus RFA (97.8%; p>0.99). Rates of OS up to 5 years and rates of disease-free survival up to 3 years were similar between groups. However, the sample size calculations were based on rates of complete ablation at 1 month, so the study may not have been adequately powered to detect differences in OS or disease-free survival.

Table 5. MWA versus RFA in Patients with Hepatic Tumors: Summary of Key RCT Characteristics

Study; Trial Countries Sites Dates Participants Interventions
          MWA RFA
Chong et al (2020)43 China 1 2011-2017 Patients age 18 or older, unresectable HCC or resectable HCC but patient opts for ablation, HCC lesion measuring 5 cm or smaller with up to 3 nodules, Child-Pugh score A or B, absence of extrahepatic metastases, absence of radiologic evidence of major vascular or bile duct invasion 47 46
Vietti Violi et al (2018)42 France, Switzerland 4 2011-2015 Patients age 18 years or older, HCC lesion measuring 4 cm or smaller with up to 3 nodules, chronic liver disease (hepatitis) or cirrhosis with Child-Pugh score A or B, and adequate pre-ablation imaging within 4 weeks before starting the intervention 76 76

HCC: hepatocellular carcinoma; MWA: microwave ablation; RFA: radiofrequency ablation; RCT: randomized controlled trial.

Table 6. MWA versus RFA in Patients with Hepatic Tumors: Summary of Key RCT Results

Study Local Tumor Progression Overall Survival Disease-free Survival Complications
  MWA vs RFA MWA vs RFA MWA vs RFA MWA vs RFA
Chong et al (2020)43        
Percentage, p NR 1 year: 97.9% vs 93.5%
3 year: 67.1% vs 72.7%
5 year: 42.8% vs 56.7%
p=0.899
1 year: 51.5% vs 58.7%
3 year: 24.1% vs 22.7%
p=0.912
Postoperative complications
2.1% vs 2.2%, p>0.999

Vietti Violi et al (2018)42
       
Percentage, p 2 year: 6% vs 12%, p=0.27 2 year: 86% vs 84%, p=0.87 NR Grade 4 complications
2% vs 0%
Grade 3 complications
0% vs 3%
Relative risk (95% CI) 2 year: 1.62 (0.66-3.94) NR NR NR

RCT: randomized controlled trial; MWA: microwave ablation; RFA: radiofrequency ablation; NR: not reported.

Table 7. Study Relevance Limitations

Study Populationa Interventionb Comparatorc Outcomesd Follow-Upe
Chong et al (2020)43 4. Included some patients with resectable disease     1. Primary outcome was rate of complete ablation at 1 month  
Vietti Violi et al (2018)42          

The study limitations stated in this table are those notable in the current review; this is not a comprehensive gaps assessment.

a Population key: 1. Intended use population unclear; 2. Clinical context is unclear; 3. Study population is unclear; 4. Study population not representative of intended use.
Intervention key: 1. Not clearly defined; 2. Version used unclear; 3. Delivery not similar intensity as comparator; 4.Not the intervention of interest.
Comparator key: 1.  Not clearly defined; 2. Not standard or optimal; 3. Delivery not similar intensity as intervention; 4. Not delivered effectively.
Outcomes key: 1. Key health outcomes not addressed; 2. Physiologic measures, not validated surrogates; 3. No CONSORT reporting of harms; 4. Not establish and validated measurements; 5. Clinical significant difference not prespecified; 6. Clinical significant difference not supported
e Follow-Up key: 1. Not sufficient duration for benefit; 2. Not sufficient duration for harms.

Table 8. Study Design and Conduct Limitations

Study Allocationa Blindingb Selective Reportingc Data Completenessd Powere Statisticalf
Chong et al (2020)43            
Vietti Violi et al (2018)42   3. Physicians not blinded   6. Analysis not intention-to-treat    

The study limitations stated in this table are those notable in the current review; this is not a comprehensive gaps assessment.

a Allocation key: 1. Participants not randomly allocated; 2. Allocation not concealed; 3. Allocation concealment unclear; 4. Inadequate control for selection bias.
Blinding key: 1. Not blinded to treatment assignment; 2. Not blinded outcome assessment; 3. Outcome assessed by treating physician.
Selective Reporting key: 1. Not registered; 2. Evidence of selective reporting; 3. Evidence of selective publication.
Data Completeness key: 1. High loss to follow-up or missing data; 2. Inadequate handling of missing data; 3. High number of crossovers; 4. Inadequate handling of crossovers; 5. Inappropriate exclusions; 6. Not intent to treat analysis (per protocol for noninferiority trials).
e Power key: 1. Power calculations not reported; 2. Power not calculated for primary outcome; 3. Power not based on clinically important difference.
Statistical key: 1. Analysis is not appropriate for outcome type: (a) continuous; (b) binary; (c) time to event; 2. Analysis is not appropriate for multiple observations per patient; 3. Confidence intervals and/or p values not reported; 4.Comparative treatment effects not calculated.

Hepatic Metastases From Primary Cancers From Other Sites
Review of Evidence
Systematic Reviews
A Health Technology Assessment by Loveman et al (2014)44 and a Cochrane review by Bala et al (2013)45 reported on ablation for liver metastasis. Reviewers found insufficient evidence to determine any benefits of MWA for liver metastasis over surgical resection.

Pathak et al (2011) conducted a systematic review of ablation techniques for colorectal liver metastases, which included 13 studies on MWA ( N=406 patients) with a minimum of 1-year follow-up.46 Mean survival rates were 73%, 30%, and 16% and ranged from 40% to 91.4%, 0% to 57%, and 14% to 32% at the 1-, 3-, and 5-year follow-ups, respectively. Minor and major complication rates were considered acceptable and ranged from 6.7% to 90.5% and 0% to 19%, respectively. Local recurrence rates ranged from 2% to 14%.

Section Summary
For individuals who have an unresectable primary or metastatic hepatic tumor who receive MWA, the evidence includes RCTs, comparative observational studies , and systematic reviews comparing MWA to RFA and to surgical resection. Relevant outcomes are OS, disease-specific survival, symptoms, QOL, and treatment-related mortality and morbidity. The body of evidence indicates that MWA is an effective option in patients for whom resection is not an option. Although studies had methodological limitations, they consistently showed that MWA and RFA had similar survival outcomes with up to 5 years of follow-up in patients with a single tumor <5 cm or up to 3 nodules <3 cm each. In a meta-analysis is of observational studies, patients receiving MWA had higher local recurrence rates and lower survival than those who received resection but the patient populations were not limited to those who had unresectable tumors. MWA was associated with lower complications, intraoperative blood loss, and hospital length of stay. The evidence is sufficient to determine the effects of the technology on health outcomes.

Unresectable Primary or Metastatic Lung Tumors
Review of Evidence
Systematic Reviews
Three systematic reviews have compared MWA to RFA for lung cancer (Tables 9 to 11).47-49

Nelson et al (2019) included 12 retrospective observational studies of MWA in patients with primary or metastatic lung tumors.49 The reviewers did not pool results due to clinical and methodological heterogeneity across the studies. The studies varied with regard to patient characteristics (tumor size, histology, number of treated nodules), outcome measures, and technical experience of surgeons performing the procedures. The primary outcome was local recurrence, and survival outcomes were not assessed. Overall, local recurrence rates ranged from 9% to 37% across the studies. Newer reports and those that targeted smaller tumors showed more favorable efficacy rates. Results in patients with multiple tumors were not reported separately. Four studies reported results by tumor size; the local recurrence rate for large tumors (> 3 or 4 cm depending on the study) were 50%, 75%, 36%, and 26%. In the same 4 studies, for small tumors (<3 or 3.5 cm depending on the study), local recurrence rates were 19%, 18%, 18%, and 5%, respectively. The most frequent adverse event with MWA was a pneumothorax requiring a chest tube. The reviewers concluded that MWA may be a useful tool in selected patients who are not ideal surgical candidates.

In a meta-analysis of observational studies, Yuan et al (2019) found higher OS for patients who received RFA compared to those who received MWA.47 However, these estimates were not directly comparable because they came from different sets of studies, and the reviewers concluded that percutaneous RFA and MWA were both effective with a high safety profile. The studies used different patient eligibility criteria (eg, tumor size, lesion number, age, follow-up). Subgroup analyses by tumor size or tumor number were not possible from the data reported.

Jiang et al (2018) conducted a network meta-analysis to determine the effectiveness of different ablation techniques in patients with lung tumors.48 Tumor size, stage of the disease, and primary versus metastatic disease were not accounted for in the analysis. For MWA, weighted average OS rates were 82.5%, 54.6%, 35.7%, 29.6%, and 16.6% at 1, 2, 3, 4, and 5 years, respectively.

Table 9. Comparison of Trials/Studies Included in SR & MA of MWA in Lung Cancer

Study Nelson et al (2019)49 Yuan et al (2019)a47 Jiang et al (2018)a48
He et al (2006)50    
Wolf et al (2008)51    
Vogl et al (2011)52  
Lu et al (2012)53  
Carrafiello et al (2013)54    
Liu et al (2013)55    
Vogl et al (2013)56  
Wei et al (2014)57    
Yang et al ( 2015)58    
Zheng et al (2014)59    
Acksteiner et al (2015)60    
Wei et al (2015)61    
Egashira et al (2016)62    
Ko et al (2016)63  
Li et al (2016)64    
Macchi et al (2017)65    
Maxwell et al (2016)66    
Vogl et al (2016)67
Zheng et al (2016)68
Healey et al (2017)69    
Nour-Eldin et al (2017)70    
Wei et al (2017)71  
Yang et al (2017)72    
Zhong et al (2017)73    

MA: meta-analysis; SR: systematic reviews.

a Studies of MWA only

Table 10. Characteristics of Systematic Reviews of MWA in Lung Cancer

Study Dates Trials Participants N (Range) Designs Duration
Nelson et al (2019)49 Up to October 3, 2017 12 Primary or secondary lung malignancies 985 (15-184) 12 retrospective observational; excluded case series with <30 lesions 9-47 months
Yuan et al (2019)47 2010-2017 12 Primary or secondary lung malignancies 800 (15-183) 12 retrospective observational Median 10-35 months (range 3-75 months), NR in 3 studies
Jiang et al (2018)48 Up to December 31, 2017 9 Primary lung cancer or pulmonary metastases from other primary tumors 438 (5-183) 1 RCT, 8 retrospective observational; excluded studies that used other treatments combined with thermal ablation Median 12-35 months (range 3-108 months)

MWA: microwave ablation; RCT: randomized controlled trial; N: sample size; NR: not reported.

Table 11. Results of Systematic Reviews of MWA in Lung Cancer 

Study Overall Survival Progression-free Survival Local Recurrence Rate Adverse Events
Nelson et al (2019)49        
Range of effect sizes NR (primary analysis was local recurrence) NR 9%-37%
25% or greater (n=4 studies); less than 25% (n=7 studies); less than 15% (n=2 studies)
7 studies found a significantly higher likelihood of local recurrence with larger tumors (>3 cm)
Pneumothorax
1%-15%
Skin burns
1.5%-6%
Periprocedural mortality
1 patient (0.5%) from ventricular tachycardia
      Local tumor progression-free  
Yuan et al (2019)47











Pooled estimate (95% CI) 1 year: 79.3% (73.7%-85.0%)
2 year: 51.9% (46.2%-57.5%)
3 year: 34.6% (26.8%-42.5%)
1 year: 64.8% (37.1%-92.4%)
2 year: 43.1% (1.5%-84.7%)
3 year: 56.0% (41.1%-70.9%)
1 year: 84.6% (72.9%-96.3%)
2 year: 68.5% (51.8%-85.1%)
3 year: 72.2% (64.5%-79.9%)
4 year: 74.1% (67.0%-81.2%)
5 year: 48.0% (23.8%-72.2%)
Pneumothorax
33.9% (23.8%-44.8%)
Pneumothorax needing intervention
11.0% (4.5%-19.7%)
Pleural effusion
9.6% (1.5%-22.4%)
Pleural effusion needing intervention
0.3% (0%-1.4%)
I2, p 1 year: I2=37.7%, p=0.155
2 year: I2=0%, p=0.691
3 year: I2=7.6%, p=0.458
1 year: I2=88.4%, p=0.003
2 year: I2=94.3%, p<0.001
3 year: NA
1 year: I2=87.9%, p<0.001
2 year: I2=81.9%, p=0.019
3 year: I2=15.1%, p=0.278
4 year: NA
5 year: NA
NA
Jiang et al (2018)48        
Weighted average 1 year: 82.5%
2 year: 54.6%
3 year: 35.7%
4 year: 29.6%
5 year: 16.6%
NR 10.9%
Major complications
22.5%

MWA: microwave ablation; CI: confidence interval; N: sample size; NA: not applicable; NR: not reported.

Randomized Controlled Trials
There is 1 RCT of MWA compared to RFA for lung tumors, conducted by Macchi et al (2017), (Tables 12 and 13).65 Patients were eligible for the study if they had a single tumor up to 5 cm, and up to 5 metastases up to 5 cm. However, at baseline, the mean tumor size was 2.21 cm (standard deviation, 0.89) in the MWA group and 1.64 cm (standard deviation, 0.80) in the RFA group. Mortality rates at 6 and 12 months did not differ between groups, and complications were significantly lower in the MWA group. Limitations of this study are summarized in Tables 14 and 15 and include its small sample size, lack of reporting on blinding, and relatively short follow-up period (12 months). Results were not reported by tumor size or the number of metastases.

Table 12. Summary of Key RCT Characteristics: MWA versus RFA in Patients with Lung Tumors

Study; Trial Countries Sites Dates Participants Interventions
          MWA RFA
Macchi et al (2017)65 Italy Multisite, NR NR Age 18 years or older; patient has tumors considered surgically inoperable, or patient did not respond to standard chemotherapy or radiotherapy, or patient refused surgery, or patient is affected by conditions with high morbidity rates that are contraindicative to surgery; maximum diameter of the primary lesion <5 cm; percutaneous accessibility of the lesion; for those with pulmonary metastases, number of metastases <5, each with maximum diameter of 5 cm







24


28

RCT: randomized controlled trial; MWA: microwave ablation; NR: not reported; RFA: radiofrequency ablation.

Table 13. Summary of Key RCT Results: MWA versus RFA in Patients with Lung Tumors 

Study Local Tumor Recurrence Survival time Mortality at 6 months Mortality at 12 months Complications
Macchi et al (2017)65          
MWA NR (graph only) 4/24 (16.7%) 4/20 (20.0%) 8/24 (33.3%)
RFA     3/28 (10.7%) 5/25 (20.0%) 16/28 (57.1%)
p-value   0.883 0.35 <0.0001 0.05

RCT: randomized controlled trial; MWA: microwave ablation; NR: not reported; RFA: radiofrequency ablation.

Table 14. Study Relevance Limitations 

Study Populationa Interventionb Comparatorc Outcomesd Follow-Upe
Macchi et al (2017)65 1. Did not report results by tumor size, histology, or number of tumors; 2. combined patients with primary and metastatic tumors in analyses     1. Local recurrence not reported 1. 12 months only

The study limitations stated in this table are those notable in the current review; this is not a comprehensive gaps assessment.

a Population key: 1. Intended use population unclear; 2. Clinical context is unclear; 3. Study population is unclear; 4. Study population not representative of intended use.
Intervention key: 1. Not clearly defined; 2. Version used unclear; 3. Delivery not similar intensity as comparator; 4.Not the intervention of interest.
Comparator key: 1.  Not clearly defined; 2. Not standard or optimal; 3. Delivery not similar intensity as intervention; 4. Not delivered effectively.
Outcomes key: 1. Key health outcomes not addressed; 2. Physiologic measures, not validated surrogates; 3. No CONSORT reporting of harms; 4. Not establish and validated measurements; 5. Clinical significant difference not prespecified; 6. Clinical significant difference not supported
e Follow-Up key: 1. Not sufficient duration for benefit; 2. Not sufficient duration for harms.

Table 15. Study Design and Conduct Limitations 

Study Allocationa Blindingb Selective Reportingc Data Completenessd Powere Statisticalf
Macchi et al (2017)65   Not reported     1. Power calculation not reported  

The study limitations stated in this table are those notable in the current review; this is not a comprehensive gaps assessment.

a Allocation key: 1. Participants not randomly allocated; 2. Allocation not concealed; 3. Allocation concealment unclear; 4. Inadequate control for selection bias.
Blinding key: 1. Not blinded to treatment assignment; 2. Not blinded outcome assessment; 3. Outcome assessed by treating physician.
Selective Reporting key: 1. Not registered; 2. Evidence of selective reporting; 3. Evidence of selective publication.
Data Completeness key: 1. High loss to follow-up or missing data; 2. Inadequate handling of missing data; 3. High number of crossovers; 4. Inadequate handling of crossovers; 5. Inappropriate exclusions; 6. Not intent to treat analysis (per protocol for noninferiority trials).
e Power key: 1. Power calculations not reported; 2. Power not calculated for primary outcome; 3. Power not based on clinically important difference.
Statistical key: 1. Analysis is not appropriate for outcome type: (a) continuous; (b) binary; (c) time to event; 2. Analysis is not appropriate for multiple observations per patient; 3. Confidence intervals and/or p values not reported; 4.Comparative treatment effects not calculated

Section Summary
For individuals who have an unresectable primary or metastatic lung tumor who receive MWA, the evidence includes 1 RCT, retrospective observational studies, and systematic reviews of these studies. Relevant outcomes are OS, disease-specific survival, symptoms, QOL, and treatment-related mortality and morbidity. The body of evidence indicates that MWA is an effective option in patients for whom resection is not an option. In the RCT, direct comparison of MWA and RFA in patients with primary or metastatic lung cancer (mean tumor size, 1.90 cm [± 0.89] at baseline) found similar mortality rates up to 12 months of follow-up. In the first of 3 systematic reviews that included 12 retrospective observational studies, local recurrence rates were similar for MWA and RFA at a range of 9 to 47 months of follow-up. In the second systematic review with a meta-analysis, there was lower OS with MWA compared to RFA, but studies were not directly comparable due to clinical and methodological heterogeneity. However, the authors concluded that percutaneous RFA and MWA were both effective with a high safety profile. In the third systematic review using a network meta-analysis, the weighted average OS rates for MWA were 82.5%, 54.6%, 35.7%, 29.6%, and 16.6% at 1, 2, 3, 4, and 5 years, respectively. Limitations of the body of evidence included a lack of controlled studies and heterogeneity across studies. The RCT did not report results by tumor size or the number of metastases. The observational studies included in the systematic reviews did not report sufficient information to assess the effectiveness or safety of MWA in subgroups based on the presence of multiple tumors or total tumor burden. Therefore, conclusions about the evidence sufficiency can only be made about patients with single tumors. For this population, the evidence is sufficient to determine the effects of the technology on health outcomes.

Unresectable Primary or Metastatic Renal Tumors
Review of Evidence
Systematic Reviews
Uhlig et al (2019) published a systematic review with meta-analyses to compare partial nephrectomy, radiofrequency ablation, cryoablation and microwave ablation and the effect on oncologic, perioperative and functional outcomes in studies published from 2005 to 2017.74 Microwave ablation was a treatment in 344 of 24, 077 patients and represented in 6 of 47 studies. The review included the single RCT (Guan 2012) which is the only study with results for all 3 outcomes of interest. No new data was included but the review utilized a network meta-analyses technique. Microwave ablation when compared to partial nephrectomy, the comparator of interest, was reported to have a lower procedural complication rate but higher local recurrence and cancer-specific mortality rates.74

In a systematic review and meta-analysis, Katsanos et al (2014) compared thermal ablation (MWA and RFA) with surgical nephrectomy for small renal tumors (mean size, 2.5 cm).75 The analysis included 1 randomized study on MWA76 (described below) and 5 cohort studies on RFA ( N=587 patients). In the ablation group, complication rates and renal function declines were significantly higher than in the nephrectomy group (p=0.04 and p=0.03, respectively). The local recurrence rate was 3.6% in both groups (relative risk, 0.92; 95% CI, 0.4 to 2.14; p=0.79) and disease-free survival up to 5 years did not differ significantly between groups (hazard ratio, 1.04; 95% CI, 0.48 to 2.24; p=0.92).

Martin et al (2013) conducted a meta-analysis comparing MWA with cryoablation for small renal tumors.77 The analysis included 7 MWA studies (n=164 patients) and 44 cryoablation studies (n=2989 patients). Selected studies were prospective or retrospective, nonrandomized, noncomparative studies. Mean follow-up duration was shorter for MWA (17.86 months) than for cryoablation (30.22 months; p=0.07). Mean tumor size was significantly larger in the MWA studies than in the cryoablation studies (2.58 cm vs. 3.13 cm, respectively, p=0.04), Local tumor progression (4.07% vs. 2.53%, respectively; p=0.46) and progression to metastatic disease (0.8% vs. 0%, respectively; p=0.12) did not differ significantly.

Randomized Controlled Trial
Guan et al (2012) reported on a prospective randomized study that compared the use of MWA with partial nephrectomy (the criterion standard of nephron-sparing surgical resection) for solitary renal tumors less than 4 cm.76 Forty-eight patients received MWA and 54 had partial nephrectomy. Patients in the MWA group (6 [23.5%]) had significantly fewer postoperative complications than in the partial nephrectomy group (18 [33.3%]; p=0.019). MWA patients also had significantly less postoperative renal function declines (p<0.009) and estimated perioperative blood loss (p<0.001) than partial nephrectomy patients. At last follow-up, estimated glomerular filtration rate declines in both groups were similar (p=1.00). Disease-specific deaths did not occur, and overall local recurrence-free survival by Kaplan-Meier estimates at 3 years was 91.3% for MWA and 96.0% for partial nephrectomy (p=0.541).

Case Series and Retrospective Reviews
Guo et al (2020) reported a retrospective review of 106 patients with 119 T1a renal cell carcinoma tumors treated with MWA.78 Complete response was achieved in 95.3% of patients (mean tumor diameter, 2.4 cm; range, 1 to 4 cm). Local tumor progression was observed in 6 patients at a mean of 20 months post-procedure. Local progression-free survival rates were 100%, 92.8%, and 90.6% at 1, 2, and 3 years, respectively. OS rates were 99%, 97.7%, and 94.6% at 1, 2, and 3 years respectively. Complications were reported in 6 patients (5.7%) within 30 days of the procedure, but none of these required intervention.

Aarts et al (2020) conducted another retrospective review of 100 patients with 108 T1 renal cell carcinomas treated with MWA.79 The median tumor size in this study was 3.2 cm (interquartile range, 2.4 to 4 cm). Primary efficacy was achieved for 81% (88/108) of lesions overall, but primary efficacy rates were lower among patients with T1b tumors (52%) versus T1a tumors (89%; p<0.001). Secondary efficacy was achieved for 97% (101/103). Over a median follow-up time of 19 months, local tumor recurrence was observed for 4 (4%) tumors.

Muto et al (2011) reported on complete tumor coagulation necrosis in 10 patients treated with MWA for clear cell renal carcinoma (median tumor size, 2.75 cm).80 No complications were reported during or after the procedure. Bai et al (2010) reported complete laparoscopic MWA in 17 of 18 clear cell renal carcinoma tumors (mean tumor size, 2.8 cm).81 In this study, evidence of disease progression was not found at a median follow-up of 20 months. Complications reported were mild (18.2%), and renal function did not significantly deteriorate.

In a study of 10 patients with solid-enhancing renal tumors (median size, 3.65 cm) who were treated with MWA, Castle et al (2011) reported tumor recurrence in 3 of 8 tumors at a mean follow-up of 17.9 months.82 Twenty percent of patients experienced intraoperative complications while 40% experienced postoperative complications, including perinephric hematoma, splenic capsular tear, pleuritic chest pain, skin burn, fever, hematuria, genitofemoral neuralgia, and urinoma.

In another study, Guan et al (2010) reported on the safety of MWA for renal hamartoma.83 In this case series, 15 of 16 patients had complete tumor ablation. Disease recurrence was not reported at a median follow-up of 16 months.

For individuals who have an unresectable primary or metastatic renal tumor who receive MWA, the evidence includes 1 RCT that compared MWA to partial nephrectomy , retrospective reviews, and case series. Relevant outcomes are OS, disease-specific survival, symptoms, QOL, and treatment-related mortality and morbidity. In the RCT, overall local recurrence-free survival at 3 years was 91.3% for MWA and 96.0% for partial nephrectomy (p=0.54). This positive outcome should be replicated in additional RCTs. There are also no controlled studies comparing MWA to other ablation techniques in patients with renal tumors. The evidence is insufficient to determine the effects of the technology on health outcomes.

Unresectable Primary or Metastatic Solid Tumors Other than Breast, Hepatic, Lung, or Renal
Review of Evidence
Systematic Reviews
No RCTs on the use of MWA for other tumors or conditions were identified. A systematic review of ablation therapies, including MWA, for locally advanced pancreatic cancer was published by Keane et al (2014).84 Reviewers found limited evidence on the use of MWA for pancreatic cancer. Cui et al (2019) conducted a non-comparative systematic review and meta-analysis of 5 retrospective studies and 2 prospective studies in patients with benign thyroid nodules or papillary thyroid microcarcinoma and found that MWA improved nodule volume and symptom scores in these patients.85

Case Series
Case studies and retrospective reviews on the use of MWA for adrenal carcinoma,86 metastatic bone tumors,87 intrahepatic primary cholangiocarcinoma,88 pancreatic neuroendocrine tumors,89 and other nononcologic conditions (ie, bleeding peptic ulcers, esophageal varices, secondary hypersplenism) were identified.

Section Summary
For individuals who have unresectable primary or metastatic solid tumors other than breast, hepatic, lung, or renal. who receive MWA, the evidence includes systematic reviews and case series. Relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The evidence is insufficient to determine the effects of the technology on health outcomes.

Summary of Evidence
For individuals who have unresectable primary or metastatic breast cancer who receive MWA, the evidence includes case series and a systematic review of feasibility and pilot studies conducted prior to 2010. Relevant outcomes are overall survival (OS), disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The evidence is insufficient to determine the effects of the technology on health outcomes.

For individuals who have an unresectable primary or metastatic hepatic tumor who receive MWA, the evidence includes randomized controlled trials (RCTs), comparative observational studies , and systematic reviews comparing MWA to radiofrequency ablation (RFA) and to surgical resection. Relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The body of evidence indicates that MWA is an effective option in patients for whom resection is not an option. Although studies had methodological limitations, results consistently showed that that MWA and RFA had similar survival outcomes with up to 5 years of follow-up in patients with a single tumor <5 cm or up to 3 nodules <3 cm each. In a meta-analysis is of observational studies, patients receiving MWA had higher local recurrence rates and lower survival than those who received resection, but the patient populations were not limited to those who had unresectable tumors. MWA was associated with lower complications, intraoperative blood loss, and hospital length of stay. The evidence is sufficient to determine the effects of the technology on health outcomes.

For individuals who have an unresectable primary or metastatic lung tumor who receive MWA, the evidence includes 1 RCT, retrospective observational studies, and systematic reviews of these studies. Relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The body of evidence indicates that MWA is an effective option in patients for whom resection is not an option. In the RCT, direct comparison of MWA and RFA in patients with primary or metastatic lung cancer (mean tumor size, 1.90 cm [± 0.89] at baseline) found similar mortality rates up to 12 months of follow-up. In the first of 3 systematic reviews that included 12 retrospective observational studies, local recurrence rates were similar for MWA and RFA at a range of 9 to 47 months of follow-up. In the second systematic review with a meta-analysis, there was lower OS with MWA compared to RFA but studies were not directly comparable due to clinical and methodological heterogeneity. However, the authors concluded that percutaneous RFA and MWA were both effective with a high safety profile. In the third systematic review using a network meta-analysis, the weighted average OS rates for MWA were 82.5%, 54.6%, 35.7%, 29.6%, and 16.6% at 1, 2, 3, 4, and 5 years, respectively. Limitations of the body of evidence included a lack of controlled studies and heterogeneity across studies. The RCT did not report results by tumor size or the number of metastases. The observational studies included in the systematic reviews did not report sufficient information to assess the effectiveness or safety of MWA in subgroups based on the presence of multiple tumors or total tumor burden. Therefore, conclusions about the evidence sufficiency can only be made about patients with single tumors. For this population, the evidence is sufficient to determine the effects of the technology on health outcomes.

For individuals who have an unresectable primary or metastatic renal tumor who receive MWA, the evidence includes 1 RCT that compared MWA to partial nephrectomy, retrospective reviews, systematic reviews and meta-analyses of the retrospective reviews (with or without the single RCT) and case series. Relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. In the RCT, overall local recurrence-free survival at 3 years was 91.3% for MWA and 96.0% for partial nephrectomy (p=0.54). This positive outcome should be replicated in additional RCTs. There are also no controlled studies comparing MWA to other ablation techniques in patients with renal tumors. The evidence is insufficient to determine the effects of the technology on health outcomes.

For individuals who have unresectable primary or metastatic solid tumors other than breast, hepatic, lung, or renal who receive MWA, the evidence includes systematic reviews and case series. Relevant outcomes are OS, disease-specific survival, symptoms, quality of life, and treatment-related mortality and morbidity. The evidence is insufficient to determine the effects of the technology on health outcomes.

Clinical Input From Physician Specialty Societies and Academic Medical Centers
While the various physician specialty societies and academic medical centers may collaborate with and make recommendations during this process, through the provision of appropriate reviewers, input received does not represent an endorsement or position statement by the physician specialty societies or academic medical centers, unless otherwise noted.

2016 Input
In response to requests, input was received from 2 physician specialty societies and 1 academic medical center while this policy was under review in 2016. This number of responses was less than optimal. Input overall was mixed. There was some support for the medical necessity of microwave ablation (MWA) in each category, with some reviewers indicating that it was standard of care for certain tumors. However, there were no indications for which all 3 reviewers agreed that MWA should be medically necessary.

2011 Input
In response to requests, input was received from 2 physician specialty societies (3 reviews) and 4 academic medical centers (6 reviews) while this policy was in development. Eight reviewers considered MWA investigational to treat primary tumors such as hepatocellular carcinoma, benign and malignant renal tumors, lung tumors, adrenal tumors, or cholangiocarcinoma. The reviewers noted insufficient evidence and a need for further studies on MWA. However, 1 reviewer indicated MWA for primary tumors, including, but not limited to hepatocellular carcinoma, benign and malignant renal tumors, lung tumors, adrenal tumors, and cholangiocarcinoma, may be considered a treatment option, and another reviewer indicated that MWA for renal tumors may be considered a treatment option.

Four reviewers considered MWA investigational to treat liver metastases, and 2 reviewers indicated MWA for liver metastases may be considered a treatment option. One reviewer noted MWA may be appropriate for tumors not amenable to radiofrequency ablation or other local treatments. This reviewer also suggested MWA may be more appropriate for tumors located near large blood vessels.

Practice Guidelines and Position Statements
National Comprehensive Cancer Network
The National Comprehensive Cancer Network guidelines on hepatobiliary cancers (v. 4.2020) list MWA (along with radiofrequency ablation, cryoablation, and percutaneous alcohol injection) as a treatment option for hepatocellular carcinoma (HCC) tumors in patients who are not candidates for potential curative treatments (eg, resection and transplantation) and do not have large-volume extrahepatic disease.90 Ablation should only be considered when tumors are accessible by percutaneous, laparoscopic, or open approaches. The guidelines indicate “ablative therapies are most effective for [HCC] tumors less than 3 cm….” HCC tumors between 3 cm and 5 cm may also be treated with ablation to prolong survival when used in combination with arterial embolization. Additionally, the tumor location must be accessible to permit ablation of the tumor and tumor margins without ablating major vessels, bile ducts, the diaphragm, or other abdominal organs. However, only 1 RCT of MWA compared to radiofrequency ablation was cited in the guidelines to support recommendations for MWA.

The guidelines on non-small cell lung cancer (v.6. 2020) do not mention MWA and state, "for medically operative disease, resection is the preferred local treatment modality (other modalities include SABR, thermal ablation such as radiofrequency ablation, and cryotherapy).91" Guidelines on small-cell lung cancer (v. 4.2020) state, "stereotactic ablative radiotherapy is an option for certain patients with medically inoperable stage I to IIA small-cell lung cancer."92

The Network guidelines on neuroendocrine tumors (v. 2.2020) state that cytoreductive surgery or ablative therapies ( ie, radiofrequency, cryotherapy, microwave) may be considered in patients with progressive hepatic-predominant metastatic disease to reduce tumor bulk and relieve symptoms of hormone hypersecretion (category 2B). Additionally, although prospective data for ablative therapy interventions are limited, the guideline notes that "percutaneous thermal ablation, often using microwave energy, can be considered for oligometastatic liver disease, generally up to 4 lesions each smaller than 3 cm."93

The guidelines on kidney cancer (v.1.2021) do not specifically address the role of MWA, but state that other thermal ablation techniques (RFA and cryotherapy) may be an option for T1 renal lesions, particularly for masses <3 cm.94

National Institute for Health and Care Excellence
The National Institute for Health and Care Excellence (2016) updated its guidance on MWA for treatment of metastases in the liver.95 The revised guidance states:  

  • Current evidence on MWA for treating liver metastases raises no major safety concerns and the evidence on efficacy is adequate in terms of tumor ablation. Therefore this procedure may be used provided that standard arrangements are in place for clinical governance, consent, and audit.

  • Patient selection should be carried out by a hepatobiliary cancer multidisciplinary team.

  • Further research would be useful for guiding the selection of patients for this procedure. This should document the site and type of the primary tumor being treated, the intention of treatment (palliative or curative), imaging techniques used to assess the efficacy of the procedure, long-term outcomes and survival.

The Institute (2007) also published guidance on MWA for HCC.96 This guidance indicated: “Current evidence on the safety and efficacy of MWA of hepatocellular carcinoma appears adequate to support the use of this procedure….” The guidance also stated there are no major concerns about the efficacy of MWA, but noted that limited, long-term survival data are available.

The Institute (2013) has published guidance on MWA for lung tumors as well97. This guidance indicated that "evidence that the procedure improves clinical outcomes and quality of life is limited in quantity and quality. There is a risk of complications, including pneumothorax, which may have serious implications for patients with already compromised lung function. Therefore this procedure should only be used with special arrangements for clinical governance, consent and audit." The guidance encourages further research.

American College of Chest Physicians
The American College of Chest Physicians’ (2013) evidence-based guidelines on the treatment of non-small-cell lung cancer noted that the role of ablative therapies in the treatment of high-risk patients with stage I non-small-cell lung cancer is evolving.98 The guidelines deal mostly with radiofrequency ablation.

American Urological Association
The American Urological Association (2017) guidelines on renal mass and localized renal cancer note that MWA remains investigational for this indication due to the the limited number of published studies and the lack of long-term follow-up data.99 Cryoablation and RFA are recommended as options for thermal ablation in patients with T1a renal masses <3 cm in size.

U.S. Preventive Services Task Force Recommendations
Not applicable.

Ongoing and Unpublished Clinical Trials
Some currently ongoing and unpublished trials that might influence this review are listed in Table 16.

Table 16. Summary of Key Trials

NCT No. Trial Name Planned Enrollment Completion Date
Ongoing      
NCT04046354 Microwave vs. Radiofrequency Ablation for Benign Thyroid Nodules: A Multicenter Randomized Controlled Trial Study 152 December 2021
NCT04081168 COLLISION XL: Unresectable Colorectal Liver Metastases (3-5cm): Stereotactic Body Radiotherapy vs. Microwave Ablation (COLLISION-XL) 68 January 2025
NCT04365751 To Compare the Efficacy of Microwave Ablation and Laparoscopic Hepatectomy for Hepatocellular Carcinoma 1,134 December 2026

NCT: national clinical trial.

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Coding Section

CodesNumberDescription
CPT   No specific codes – see Policy Guidelines
  32998 Ablation therapy for reduction or eradication of 1 or more pulmonary tumor(s) including pleura or chest wall when involved by tumor extension, percutaneous, including image guidance when performed radiofrequency, unilateral
  47382 Ablation, 1 or more liver tumor(s), percutaneous, radiofrequency
  50592 Ablation, 1 or more renal tumor(s), percutaneous, unilateral, radiofrequency
  76940 Ultrasound guidance for, and monitoring of, parenchymal tissue ablation
HCPCS C9751 Bronchoscopy, rigid or flexible, transbronchial ablation of lesion(s) by microwave energy, including fluoroscopic guidance, when performed, with computed tomography acquisition(s) and 3-d rendering, computer-assisted, image-guided navigation, and endobronchial ultrasound (ebus) guided transtracheal and/or transbronchial sampling (eg, aspiration[s]/biopsy[ies]) and all mediastinal and/or hilar lymph node stations or structures and therapeutic intervention(s)
ICD-10-CM   Investigational for all primary and metastatic tumors.
  C22.0 Liver cell carcinoma
  C22.2 Hepatoblastoma
  C22.3 Angiosarcoma of liver
  C22.4 Other sarcomas of liver
  C22.7 Other specified carcinomas of liver
  C22.8 Malignant neoplasm of liver, primary, unspecified as to type
  C22.9 Malignant neoplasm of liver, not specified as primary or secondary
  C50.011-C50.929 Malignant neoplasm of breast, code range
  C64.1-C65.9 Malignant neoplasm of kidney, code range
  C7A.093 Malignant carcinoid tumor of the kidney
  C7B.02 Secondary carcinoid tumors of liver
  C78.7 Secondary malignant neoplasm of liver and intrahepatic bile duct
  C79.00-C79.02 Secondary malignant neoplasm of kidney and renal pelvis
  D37.6 Neoplasm of uncertain behavior of liver, gallbladder and bile ducts
  D41.00-D41.02 Neoplasm of uncertain behavior of kidney
  D41.10-D41.12 Neoplasm of uncertain behavior of renal pelvis
ICD-10-PCS   ICD-10-PCS codes are only used for inpatient services. There is no specific ICD-10-PCS code for this procedure.
  0F500ZZ, 0F510ZZ, 0F520ZZ, 0F503ZZ, 0F513ZZ, 0F523ZZ, 0F504ZZ, 0F514ZZ, 0F524ZZ Destruction, hepatobiliary system and pancreas, liver, open, percutaneous or percutaneous endoscopic approaches, code list
  0H5T0ZZ, 0H5T3ZZ, 0H5TXZZ, 0H5U0ZZ, 0H5U3ZZ, 0H5UXZZ,0H5V0ZZ, 0H5V3ZZ, 0H5VXZZ Destruction, breast, open, percutaneous or external approaches, code list
  0T500ZZ, 0T503ZZ, 0T504ZZ, 0T508ZZ, 0T510ZZ, 0T513ZZ, 0T514ZZ, 0T518ZZ, 0T530ZZ, 0T533ZZ, 0T534ZZ, 0T538ZZ, 0T540ZZ, 0T543ZZ, 0T544ZZ, 0T548ZZ Destruction, urinary system, kidney, open, percutaneous, percutaneous endoscopic, or via natural or artificial opening endoscopic approaches, code list
Type of service Surgery  
Place of service Outpatient/Inpatient

Procedure and diagnosis codes on Medical Policy documents are included only as a general reference tool for each policy. They may not be all-inclusive.  

This medical policy was developed through consideration of peer-reviewed medical literature generally recognized by the relevant medical community, U.S. FDA approval status, nationally accepted standards of medical practice and accepted standards of medical practice in this community, Blue Cross and Blue Shield Association technology assessment program (TEC) and other non-affiliated technology evaluation centers, reference to federal regulations, other plan medical policies, and accredited national guidelines.

"Current Procedural Terminology © American Medical Association.  All Rights Reserved" 

History From 2013 Forward     

12/01/2020 

Annual review, no change to policy intent. Updating guidelines, coding, rationale and references. 

12/9/2019 

Annual review, expanding coverage to include medical necessity criteria for lung and liver tumors in some instances. Also updating background, description, regulatory status, rationale and references. 

12/20/2018 

Annual review, no change to policy intent. Updating rationale and references. 

12/12/2017 

Annual review, no change to policy intent. Updating description, rationale and references. 

12/05/2016 

Annual review, no change to policy intent. Updating background, description, guidelines, rationale and references. 

12/15/2015 

Annual review, no change to policy intent. 

12/09/2014 

Annual review, no change to policy intent. Added coding and policy guidelines. Updated rationale,references and description. 

12/4/2013

Annual review.  Updated rationale and references.  Added related policies and benefit applications.


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