Moustafa Abdalla1, Amelia T. Collings2, Rebecca Dirks2, Edwin Onkendi3, Daniel Nelson4, Emily Miraflor5, Faique Rahman6, Ahmad Ozair7, Jake Whiteside2, Mihir M Shah8, Subhashini Ayloo9, Ahmed Abou-Setta10, Iswanto Sucandy11, Ali Kchaou12, Samuel Douglas13, Patricio Polanco14, Timothy Vreeland15, Joseph Buell16, Mohammed T. Ansari17, Aurora D. Pryor18, Bethany J. Slater19, Ziad Awad20, William Richardson21, Adnan Alseidi22, D. Rohan Jeyarajah23, Eugene Ceppa2
- Department of Surgery, Harvard Medical School, Boston, MA, USA
- Department of Surgery, Indiana University School of Medicine, Indianapolis, IN, USA
- Department of Surgery, Texas Tech University Health Sciences, TX, USA
- Department of Surgery, William Beaumont Army Medical Center, Fort Bliss, TX, USA
- Department of Surgery, University of California, San Francisco – East Bay, CA, USA
- Jawaharlal Nehru Medical College and Hospital, Aligarh Muslim University, Aligarh, India
- King George’s Medical University, Chowk, Lucknow, India
- Division of Surgical Oncology, Department of Surgery, Emory University School of Medicine, Winship Cancer Institute, Atlanta, GA, USA
- Department of Surgery, Alpert Medical School of Brown University, Providence, RI, USA
- Knowledge Synthesis, University of Manitoba, Winnipeg, Canada
- Department of Surgery, University of Central Florida, Tampa, FL, USA
- Department of Surgery, University of Sfax, Sfax, Tunisia
- Sentara Medical Group, Norfolk, VA. USA
- University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Surgery, Brooke Army Medical Center, Houston, TX, USA
- Department of Surgery and Pediatrics, Tulane University, New Orleans, LA USA
- School of Epidemiology and Public Health, University of Ottawa, Ontario, Canada
- Department of Surgery, Renaissance School of Medicine, Stony Brook University, Stony Brook, NY, USA
- Department of Surgery, University of Chicago, IL, USA
- Department of Surgery, University of Florida College of Medicine-Jacksonville, Jacksonville, FL, USA
- Department of Surgery, Ochsner Clinic, New Orleans, LA, USA
- Department of Surgery, University of California San Francisco, CA, USA
- Department of Surgery, TCU and UNTHSC School of Medicine, Fort Worth, TX, USA
Address all correspondences to::
Eugene P. Ceppa, MD
Associate Professor of Surgery
Indiana University School of Medicine
Background: Primary hepatocellular carcinoma (HCC) and colorectal liver metastases (CRLM) represent the two most common malignant neoplasms of the liver. The objective of this study was to assess outcomes of surgical approaches to liver ablation comparing laparoscopic versus percutaneous microwave ablation (MWA), and MWA versus radiofrequency ablation (RFA) in patients with HCC or CRLM lesions smaller than 5cm.
Methods: A systematic review was conducted across seven databases, including PubMed, Embase and Cochrane, to identify all comparative studies between 1937-2021. Two independent reviewers screened for eligibility, extracted data for selected studies, and assessed study bias using the modified Newcastle Ottawa Scale. Random effects meta-analyses were subsequently performed on all available comparative data.
Results: From 1066 records screened, 11 studies were deemed relevant to the study and warranted inclusion. Eight of the 11 studies were at high or uncertain risk for bias. Our meta-analyses of two studies revealed that laparoscopic MW ablation had significantly higher complication rates compared to a percutaneous approach (risk ratio = 4.66; 95% confidence interval = [1.23, 17.22]), but otherwise similar incomplete ablation rates, local recurrence, and oncologic outcomes. The remaining nine studies demonstrated similar efficacy of MWA and RFA, as measured by incomplete ablation, complication rates, local/regional recurrence, and oncologic outcomes, for both HCC or CRLM lesions less than 5cm (p > 0.05 for all outcomes). There was no statistical subgroup interaction in the analysis of tumors <3cm.
Conclusions: The available comparative evidence regarding both laparoscopic versus percutaneous MWA and MWA versus RFA is limited, evident by the few studies that suffer from high/uncertain risk of bias. Additional high-quality randomized trials or statistically matched cohort studies with sufficient granularity of patient variables, institutional experience, and physician specialty/training will be useful in informing clinical decision making for the ablative treatment of HCC or CRLM.
Key Words: microwave ablation; percutaneous; laparoscopic; radiofrequency ablation; hepatocellular carcinoma; colorectal liver metastases
Hepatectomy remains the gold standard treatment for the two most common malignant neoplasms of the liver, primary hepatocellular carcinoma (HCC) and colorectal liver metastases (CRLM)[1-3]. Unfortunately, when considering both contraindications to surgical treatment (e.g., insufficient future liver remnant, tumor size, number, anatomic distribution) and comorbid conditions that increase surgical morbidity, less than 5-20% of patients are suitable candidates for resection[2-6]. Furthermore, the improvement in long-term prognosis has been modest: the 5-year survival rate is estimated at 20-40%[2, 3]. This is especially concerning given the increasing incidence of primary HCC since the 1990s and the fact that 25-50% of patients with colorectal cancer will develop CRLM[8-10].
The development of (minimally invasive) techniques for tumor ablation by direct application of chemicals or energy have addressed some of these shortcomings, especially for lesions that are less than 5cm [2, 11-14]. With the reduced morbidity and mortality compared to resection, these techniques have expanded the pool of eligible patients, can be used to treat small tumor sizes/multiple tumors, and if clinically indicated, may be repeated to treat recurring tumors. Thermal modalities, including radiofrequency (RFA) and microwave (MWA) ablation, represent the most widely-used ablative techniques. RFA treatment is the most common and an accepted approach in selected patients (e.g., HCC lesions smaller than 3cm) [12, 13, 15]. In contrast, MWA, a more recent addition initially developed for lung cancers, has some theoretical benefits over RFA (including less peri-procedural pain, and more predictable ablation)[11-14].
Although both RFA and MWA result in coagulative necrosis via direct application of heat, the physical principles employed are distinct[4, 11-13]. RFA creates a zone of coagulation necrosis through both resistive heating derived from an alternating current driven from the applicator probe (cathode), as well as an accompanying thermal diffusion into adjacent tissues[4, 11]. Comparatively, MWA uses dielectric (electromagnetic) hysteresis which can penetrate tissue that are generally recognized as poor electrical conduits and is generally less reliant on conduction down the thermal gradient (i.e., less indirect application of heat). MWA can generate more power to produce larger and higher ablation temperatures, but at an increased risk of other complications not as commonly associated with RFA (e.g., thrombosis of the portal vein in cirrhotic patients). Despite our understanding of these physical principles and several systematic reviews on these ablative techniques[2-4, 16], it is unclear how the two modalities and technical variations thereof (laparoscopic, percutaneous, open) compare with respect to procedural-specific morbidity, local/regional recurrence, and survival.
To explore the comparative effectiveness of microwave and radiofrequency ablation, as well as to assess the benefit of percutaneous versus laparoscopic microwave ablation, we conducted a systematic review and meta-analysis to inform our combined Society of American Gastrointestinal and Endoscopic Surgeons (SAGES) and Americas Hepato-Pancreato-Biliary Association (AHPBA) guidelines and ultimately help clinicians in selecting ablative treatment modalities for individuals afflicted with primary or secondary liver neoplasms.
METHODS AND MATERIALS
To compare the two aforementioned modalities, the SAGES guidelines committee and representatives from AHPBA formed a working group to perform a systematic review and meta-analysis reported here according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The subgroup had originally drafted six questions according to the PICO format (Population, Intervention, Comparator, and Outcomes) to guide the literature search (see Appendix 1 – Note 1). However, on completion of the literature search, the working group realized that only sufficient evidence existed to answer two modified questions as follows:
Key Question 1 (KQ1): Should Percutaneous vs. Laparoscopic MW ablation be used for HCC and/or CRLM less than 5cm?
Outcomes: Incomplete Ablation, Local/Regional Recurrence, Complications, Disease Free Survival (DFS), Overall Survival (OS
Key Question 2 (KQ2): Should MW ablation (laparoscopic or open) vs. RF ablation (laparoscopic or open) be used for HCC or CRLM less than 5cm?
Subgroup analysis: HCC or CRLM less than 3cm
Outcomes: Incomplete Ablation, Local/Regional Recurrence, Complications, DFS, OS
Types of interventions
As described above, all studies comparing percutaneous versus laparoscopic MWA of HCC or CRLM were included, as were any comparative studies of surgical approaches to MWA and RFA (including laparoscopic or open) for the same tumors. Studies that included combined chemoembolization and ablation were also included but tagged for possible source of heterogeneity. Any studies that combined resection with ablation were excluded from our meta-analysis.
Types of Outcomes
Five classes of outcomes of interest were specified a priori: (i) incomplete ablation, defined as the number of tumors incompletely ablated out of the total number of tumors (not individual patients); (ii) perioperative complications of Clavien-Dindo grade ≥3; (iii) local/regional recurrence, defined as radiologic and/or histologic identification of recurrent tumor at original site or draining lymph nodes after completed ablation; (iv) disease-free survival; and (v) overall survival.
Literature Search & Eligibility Criteria
A clinically guided search was performed for each of the six key questions (Appendix 1 – Note 1) in December 2019, with the assistance of a medical librarian, across seven databases: the Cochrane library, Clinicaltrials.gov, the Cumulative Index to Nursing and Allied Health Literature (CINAHL), Embase, PubMed, the WHO’s International Clinical Trials Registry Platform (ICTRP), and Google Scholar. The full search criteria and the number of records contributed from each database is provided in Appendix 1 – Note 2, including all publications between 1937-2021. All records were combined with EndNote (Clarivate Analytics) then uploaded to Covidence for screening, with duplicates automatically removed in both EndNote and Covidence prior to screening. Exclusion criteria included: reviews that are not systematic reviews and/or meta-analyses, non-English abstracts, non-comparative studies (e.g. case series), and total sample sizes of less than 10 patients across all arms (e.g., case reports or limited case series). An updated search was performed in June 2021 to capture more recent studies or studies not included in the original search.
All reviewers participating in the systematic review had received prior training in systematic review methodology. To calibrate reviewers’ ratings for study selection and screening, 100 randomly selected abstracts were reviewed by all reviewers on Abstrackr (Brown University, Providence, Rhode Island). All disagreements were discussed during a conference call. Subsequently, all titles and abstracts were screened by two independent reviewers for relevance and eligibility using Covidence. All irrelevant publications were excluded, as were any remaining duplicates or non-English language studies that bypassed our search filters. Full text review by two independent reviewers was subsequently performed. Exclusion criteria included non-comparative studies, case reports, letters to the editors, abstracts, author replies, and lay press articles Only peer-reviewed English language manuscripts meeting screening criteria were included in our final data extraction. It is also important to note that, while reviews were excluded from the pooled analyses, the reference lists were hand-searched for additional relevant references. Discrepancies were resolved through discussion among the reviewers, with a final decision made by the senior author (E.C.) when necessary.
Risk of bias in individual studies
The modified Newcastle-Ottawa Scale was used to assess risk of bias for observational studies (Appendix 1 – Note 3) . Each study was scored by two independent reviewers. Criteria were assessed for risk of bias across three broad categories: selection, comparability, and outcomes. Our minimum length of follow up to be considered ‘low risk of bias’ from outcomes was a priori defined as 1 year, with length of follow up 3 years or greater as ideal. No randomized control trials were selected for full data extraction, and thus, the Cochrane Risk of Bias Tool was not employed in this systematic review.
Two reviewers independently completed the data extraction forms on Covidence to extract study characteristics, sponsorship source, methods, population (including baseline characteristics), interventions, and a priori determined outcomes. Our primary outcomes, as described above in detail, were incomplete ablation, local/regional recurrence, complication rates, disease-free survival, and overall survival.
Study data were synthesized quantitatively. We used RevMan (version 5.4 Nordic Cochrane Centre, Copenhagen, Denmark) for meta-analyses. As all relevant data were dichotomous, we estimated risk ratios (RR) with a Mantel-Haenszel (MH) random effects model. Heterogeneity between studies was assessed using I2 and χ2 measures. A p < 0.05 was considered significant for χ2 values; a I2 < 40% was considered low. We meta-analyzed data when heterogeneity across studies was low or remained unexplained.
Across the bibliographic databases and the 33 records identified through hand searching of systematic review reference lists, total 1066 unique records were screened for eligibility with 11 records deemed relevant to the two review questions (PRIMSA flow diagram Figure 1). Each record represented a unique study. All 11 studies were of observational design (see Table 1 and Table 2).
Figure 1. PRISMA flow diagram for the systematic review. The breakdown by question is summarized in Tables 1 and 2.
Table 1. Baseline characteristics of the two studies included to answer KQ1 (percutaneous versus laparoscopic MW ablation). Both studies are retrospective cohort studies from Italian groups that did not have any sponsors listed. No patient from either study underwent embolization. DeCobelli 2017 included both HCC and CRLM, as well as liver metastases from neuroendocrine tumors, pancreatic cancer, lung cancer, and urothelial cancer. DellaCorte 2020 included only HCC patients.
Abbreviations: Microwave ablation, MWA.
For DeCobelli 2017: Inclusion criteria for primary liver tumors included the presence of a potentially curable liver-confined disease, disease unsuitable to hepatic resection alone due to inadequate functional liver reserve, according to EASL–EORTC guidelines. Inclusion criteria for liver metastases included curative intent of liver-confined disease, contraindication to surgery, and local liver disease control when other treatments such as radiotherapy or chemotherapy were applied to an extrahepatic tumor site. Exclusion criteria were pregnancy, the presence of refractory ascites or coagulopathies not susceptible of medical correction.
For DellaCorte 2020: Inclusion criteria included clinical and imaging evidence of HCC (radiological diagnosis of tumors on pre-operative dynamic contrast-enhanced CT or MRI with a liver-specific acquisition protocol); disease stage 0, A, B deemed amenable of curative treatment (ablation alone or ablation combined with surgery); ablation within one month of last imaging.
For DeCobelli 2017: Even though no comparative analysis was done for the groups of interest (percutaneous ablation vs laparoscopic ablation) to check for any group differences, the authors mention that to verify possible confounding effects, a multivariate constrained mixed effect model of the AZ volume as a function of liver condition and operative approach was fitted. The other independent variables considered in this study (sex, age, proximity to capsule and vessels) showed no evidence of improvement when added to the model.
For DellaCorte 2020: Compared to LMWA, PWMA had more patients who had previous HCC treatment, less patients treated under general anesthesia, more patients with chronic hepatitis C and less with “idiopathic” as the cause of cirrhosis, more patients with BCLC stage A1 and fewer patients with stage A4 or multifocal disease. A higher amount of energy over tumor size was delivered in laparoscopic ablation. All these group differences were statistically significant (p < 0.05).
Table 2. Baseline characteristics of the 9 studies included to answer KQ2 (Surgical MWA vs. Surgical RFA). No sponsors or funding sources were reported for any of the studies.
Abbreviations (alphabetical order): Colorectal metastases, CRLM; hepatocellular carcinoma, HCC; microwave ablation, MWA; radiofrequency ablation, RFA; standard deviation, SD.
* In Lee 2017: Two patients received TACE as treatment for residual disease.
Inclusion and exclusion criteria for each study, as well as a brief discussion of group differences between interventions and tumor locations, is available in Appendix 1 – Note 4.
Key Question 1 (KQ1): Should Percutaneous vs. Laparoscopic MW ablation be used for HCC and/or CRLM less than 5cm?
A total of two observational studies, with 81 and 91 patients who underwent liver-directed microwave thermal ablations, met inclusion criteria for KQ1[19, 20]. Unfortunately, both studies were deemed to have a high risk of bias for all outcomes, driven primarily by poor comparability between intervention groups and inadequately defined follow-up periods (Table 3).
Table 3. Risk of bias for the observational studies included under KQ1 as assessed by a modified Newcastle Ottawa Scale.
Incomplete Ablation: Both studies were included in the meta-analysis for incomplete ablation. Data from 54 laparoscopic and 97 percutaneous MW ablations demonstrated a lower risk of incomplete ablation after the laparoscopic approach, although this was not statistically significant (RR 0.28, 95% CI 0.05-1.55, I2 0%, Figure 2).
Figure 2. Forest plot for incomplete ablation with percutaneous MWA as the reference class
Complications: While neither study was independently significant, meta-analysis revealed an increased MH risk ratio for complications in laparoscopic, versus percutaneous, microwave ablation (risk ratio [RR] = 4.66; 95% confidence interval [CI] = [1.23, 17.22]; Figure 3).
Figure 3. Forest plot for complication rates of laparoscopic versus percutaneous MW ablation
Local/regional recurrence; 1-year disease-free survival; 1-year overall survival: Only one of the two studies merited inclusion in meta-analyses for the three aforementioned outcomes; all were non-significant in comparisons of laparoscopic versus percutaneous MWA (Figure 4). Our limitation to outcomes at 1 year was dictated exclusively by the availability of data (i.e., no outcome data beyond 1 year).
Figure 4a. Forest plot with percutaneous MWA as the reference class for local/regional recurrence.
Figure 4b. Forest plot with percutaneous MWA as the reference class for disease-free survival at 1 year.
Figure 4c. Forest plot with percutaneous MWA as the reference class for overall survival at 1-year.
Key Question 2 (KQ2): Should MW ablation (laparoscopic or open) vs. RF ablation (laparoscopic or open) be used for HCC or CRLM less than 5cm?
Nine comparative studies met inclusion criteria for KQ2 [21-29]. Six of the nine total studies were deemed to have high or uncertain risk of bias (Table 4). The study cohorts ranged from 35 to 391 patients (Table 2).
Table 4. Risk of bias for the observational studies included under KQ2 (MWA vs RFA for lesions smaller than 5cm), as assessed by a modified version of the Newcastle Ottawa Scale.
Incomplete Ablation: Six of nine studies, with data from 348 MWA and 367 RFA, were included in the combined less than 5cm meta-analysis and revealed no difference between MWA and RFA (RR 1.0, 95% CI 0.05-1.55, I2 0%, Figure 5). While the subgroup analysis for tumor less than 3cm favored MWA, it included one study and was not significant (RR 0.19, 95% CI 0.01-3.88, Figure 5).
Figure 5. Forest plot for incomplete ablation with RFA as the reference class.
Complications: Similarly, eight of nine studies, with data from 402 MWA and 480 RFA, were included in the combined less than 5cm meta-analysis and revealed no difference between MWA and RFA (RR 1.0, 95% CI 0.05-1.55, I2 0%, Figure 6). This was consistent for all subgroup analyses, including tumors less than 3cm (RR 0.78, 95% CI 0.72-1.33, I2 0%, Figure 6).
Figure 6. Forest plot for complication rates with RFA as the reference class.
Local/regional recurrence; disease-free survival; overall survival: All comparative meta-analyses between MWA and RFA were non-significant for the three aforementioned outcomes explored in both the cumulative (< 5cm) and sub-group (< 3cm) analyses (Figures 7-9). That is, there were no significant differences between patients who underwent MWA versus RFA with regards to local/regional recurrence (combined MH RR = 0.97, 95% CI 0.73-1.30, I2=0%; Figure 7). There were also no significant differences for disease-free survival at 1 year (combined MH RR = 0.99, 95% CI = 0.83-1.19, I2=15%), 3 years (RR = 1.03, 95% CI = 0.73-1.45, I2=0%), and 5 years (RR = 1.09, 95% CI = 0.79-1.51, I2=0%; Figure 8). Similarly, we observed no significant differences in the metanalyses for overall survival at 1 year (RR = 0.99, 95% CI = 0.97-1.01, I2=7%), 3 years (RR = 0.99, 95% CI = 0.94-1.05, I2=0%), and 5 years (RR = 1.01, 95% CI = 0.91-1.11, I2=0%; Figure 9).
Figure 7. Forest plot for local/regional recurrence with RFA as the reference class.
Figure 8a. Forest plot for DFS with RFA as the reference class at 1 year.
Figure 8b. Forest plot for DFS with RFA as the reference class at 3 years.
Figure 8c. Forest plot for DFS with RFA as the reference class at 5 years.
Figure 9a. Forest plot for OS with RFA as the reference class a 1 year.
Figure 9b. Forest plot for OS with RFA as the reference class at 3 years.
Figure 9c. Forest plot for OS with RFA as the reference class at 5 years.
The purpose of this systematic review was to review the literature and pool appropriate comparative data to better inform clinical decision making regarding both the ablative modality and technical approach for the treatment of the two most common malignant liver neoplasms. Despite a comprehensive literature search, we identified less than a dozen relevant studies with the majority at high or uncertain risk of bias. Within these constraints, we noted that the efficacy of MWA, as measured by incomplete ablation, complication rates, local/regional recurrence, and survival, appears similar to that of RFA both for HCC and CRLM lesions less than 5cm. This was consistent in the subgroup analysis of lesions less than 3cm. With regards to approach, laparoscopic MWA had significantly higher complication rates, but otherwise similar risk of incomplete ablation, local/regional recurrence, and survival.
Relationship to literature. There have been several comparative studies [30, 31, 32] and systematic reviews [33-35] that have attempted to address outcomes (including local disease control and survival) of percutaneous MWA versus RFA for HCC and CRLM. While most of these studies hint at similar completion frequencies, complication rates, and survival between MWA and RFA, they disagree with regards to local tumor control and progression[33, 34]. This controversy, in part, stems from substantial variation in the clinical contexts in which these ablation technologies were deployed (e.g., tumor size, number, anatomic distribution, as well as patient profiles/comorbidities), making it difficult to compare or to perform a meta-analysis of the results. Further, none of these studies have explored other surgical approaches (e.g., laparoscopic, or open). Our analyses here suggest that laparoscopic or open MWA and RFA are similarly safe and effective for lesions smaller than 5cm. However, given the limited evidence and quality, these results are not definitive. In contrast, very few studies have compared percutaneous and laparoscopic MWA of malignant liver neoplasms[19, 20]. Thus, while this limits the power of our meta-analysis, our systematic review provides a comprehensive look at the existing literature. Our results suggest that percutaneous MWA is safer than laparoscopic MWA, with regards to complication rates, but no difference in ablative completeness rates or survival. Although given the major differences in patients included in each cohort (including more multifocal disease patients in the laparoscopic group, as well as overall sicker patients with higher incidence of chronic hepatitis C), it is unclear how confounded these observations are.
Limitations. All 11 comparative studies included in our analyses were observational (all but one being retrospective cohort studies), with relatively small sample sizes and short follow-up. Furthermore, the majority (two out of two of the percutaneous versus laparoscopic MWA studies, and five of nine of the MWA vs RFA studies) were deemed at either uncertain or high risk of bias. No randomized clinical trials met our inclusion criteria. Altogether, the paucity of high-quality evidence limits the definitive with which we can present these conclusions. Restrictions in our literature search (e.g., to English language only studies) are likely to have had minimal impact, given both the national/geographic diversity of the included studies (China, Egypt, Italy, Japan, and USA) and that only two full text articles were excluded (Figure 1).
Relevance to clinical practice. Our findings suggest MWA and RFA for HCC or CRLM lesions less than 5cm are comparable with respect to efficacy and safety. Further, our results also support that percutaneous MWA should be preferred to laparoscopic approaches due to lower complication rates. However, as discussed above, given the limited evidence and quality of data, these results do not definitively eliminate the clinical equipoise surrounding our PICO questions.
Future research recommendations. Given the paucity of comparative observational studies and the complete absence of randomized control trials, there is a pressing need for higher-quality evidence to inform both selection of the ablative technology and technical approach. This evidence must have adequately sufficient follow-up and must clearly define the clinical contexts/indications (if any) in which one approach or technique may be preferred over another (e.g., tumor size or anatomic distribution). We encourage researchers to ensure sufficient granularity in the data (e.g., molecular biology, location, experience of institution, and physician specialty [e.g., interventional radiology vs surgery]) to help discriminate between institutional and intervention effects, as well as identify appropriate patients for each intervention.
Available evidence indicates that there was no difference between MWA and RFA treatment with a surgical (laparoscopic or open) approach for HCC or CRLM lesions less than 5cm, with respect to safety or efficacy. Further, percutaneous MWA is preferable to laparoscopic approaches due to lower complication rates but is otherwise comparable with respect to completeness rates and survival. Our systematic review also revealed a definitive need for high quality comparative/population-based studies to better guide clinical decision making. While the evidence is limited and of variable quality, the results described here will form the basis of an upcoming integrated SAGES-AHPBA clinical practice guideline.
Liver Ablation Systematic Review Appendix 1
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- Facciorusso A, Di Maso M, Muscatiello N (2016) Microwave ablation versus radiofrequency ablation for the treatment of hepatocellular carcinoma: A systematic review and meta-analysis. Int J Hyperthermia 32:339-344
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Guidelines for clinical practice are intended to indicate preferable approaches to medical problems as established by experts in the field. These recommendations will be based on existing data or a consensus of expert opinion when little or no data are available. Guidelines are applicable to all physicians who address the clinical problem(s) without regard to specialty training or interests, and are intended to indicate the preferable, but not necessarily the only acceptable approaches due to the complexity of the healthcare environment. Guidelines are intended to be flexible. Given the wide range of specifics in any health care problem, the surgeon must always choose the course best suited to the individual patient and the variables in existence at the moment of decision.
Guidelines are developed under the auspices of the Society of American Gastrointestinal and Endoscopic Surgeons and its various committees, and approved by the Board of Governors. Each clinical practice guideline has been systematically researched, reviewed and revised by the guidelines committee, and reviewed by an appropriate multidisciplinary team. The recommendations are therefore considered valid at the time of its production based on the data available. Each guideline is scheduled for periodic review to allow incorporation of pertinent new developments in medical research knowledge, and practice.