Practice guidelines for ultrasound-guided percutaneous microwave ablation for hepatic malignancy

Experimental study for in vitro prostate cancer treatment with microwave ablation and pulsed electromagnetic field

This paper presents the findings of a comprehensive study exploring the synergistic effects arising from the combination of microwave ablation and pulsed electromagnetic field (PEMF) therapy on prostate cancer cells. The research encompassed five distinct experimental groups, with continuous electric field measurements conducted during the entire treatment process. Group 1 and Group 2, subjected to microwave power below 350 W, exhibited specific electric field values of 72,800 V/m and 56,600 V/m, respectively. In contrast, Group 3 and Group 4, exposed to 80 W microwave power, displayed electric field levels of approximately 1450 V/m, while remaining free from any observable electrical discharges. The migratory and invasive capacities of PC3 cells were assessed through a scratch test in all groups. Notably, cells in Group 3 and Group 4, subjected to the combined treatment of microwave ablation and PEMF, demonstrated significantly accelerated migration in comparison to those in Groups 1 and 2. Additionally, Group 5 cells, receiving PEMF treatment in isolation, exhibited decreased migratory ability. These results strongly suggest that the combined approach of microwave ablation and PEMF holds promise as a potential therapeutic intervention for prostate cancer, as it effectively reduced cell viability, induced apoptosis, and impeded migration ability in PC3 cells. Moreover, the isolated use of PEMF demonstrated potential in limiting migratory capacity, which could hold critical implications in the fight against cancer metastasis.

Complication Rates and Risk of Recurrence After Percutaneous Radiofrequency Ablation and Microwave Ablation for the Treatment of Liver Tumors: a Meta-analysis

RATIONALE AND OBJECTIVES

The rate of complications and risk of local recurrence following percutaneous radiofrequency ablation (RFA) and microwave ablation (MWA) for liver tumors varies significantly between investigations. This meta-analysis aimed to assess complication rates and risk of local recurrence after percutaneous RFA and MWA.

MATERIALS AND METHODS

PubMed, Medline, Web of Science, the Cochrane Library, Embase, Google Scholar, and CINAHL were systematically searched from database inception until August 2022 to retrieve articles reporting the complication rates and risk of recurrence after percutaneous RFA and MWA for the treatment of liver tumors. Pooled odds ratios (OR) with 95% confidence intervals (CI) were calculated and displayed by forest plots. To measure heterogeneity, Cochran Q and I2 statistics were also applied. Egger's test and funnel plots were also performed to assess any potential publication bias. Additionally, subgroup analysis was done to investigate the source of heterogeneity.

RESULTS

26 studies including 2026 and 1974 patients for RFA and MWA, respectively, were included. The rate of minor complications was significantly higher after MWA compared to RFA, yielding an overall OR of 0.688 (95% CI: 0.549-0.862, P = 0.001). Similarly, the rate of major complications was significantly higher after MWA than RFA (P = 0.012), yielding an overall OR of 0.639 (95% CI: 0.450-0.907). No significant difference was found between RFA and MWA in terms of local recurrence after ablation (P > 0.05). In addition, there was no statistical evidence of publication bias.

CONCLUSION

When most factors are considered equally, percutaneous RFA and MWA can be considered safe modalities for the treatment of liver tumors, with RFA superior in terms of the incidence of minor and major complications.

Microwave coagulation for liver metastases

BACKGROUND

Liver metastases (i.e. secondary hepatic malignancies) are significantly more common than primary liver cancer. Long-term survival after radical surgical treatment is approximately 50%. For people in whom resection for cure is not feasible, other treatments must be considered. One treatment option is microwave coagulation utilising electromagnetic waves. It involves placing an electrode into a lesion under ultrasound or computed tomography guidance.

OBJECTIVES

To evaluate the beneficial and harmful effects of microwave coagulation versus no intervention, other ablation methods, or systemic treatments in people with liver metastases regardless of the location of the primary tumour.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest date of search was 14 April 2023.

SELECTION CRITERIA

Randomised clinical trials assessing beneficial or harmful effects of microwave coagulation and its comparators in people with liver metastases, irrespective of the location of the primary tumour. We included trials no matter the outcomes reported.

DATA COLLECTION AND ANALYSIS

We followed standard Cochrane methodological procedures. Our primary outcomes were: all-cause mortality at the last follow-up and time to mortality; health-related quality of life (HRQoL); and any adverse events or complications. Our secondary outcomes were: cancer mortality; disease-free survival; failure to clear liver metastases; recurrence of liver metastases; time to progression of liver metastases; and tumour response measures. We used risk ratios (RR) and hazard ratios (HR) with 95% confidence intervals (CI) to present the results. Two review authors independently extracted data and assessed the risk of bias using the Cochrane RoB 1 tool. We used GRADE methodology to assess the certainty of the evidence.

MAIN RESULTS

Three randomised clinical trials fulfilled the inclusion criteria. The control interventions differed in the three trials; therefore, meta-analyses were not possible. The trials were at high risk of bias. The certainty of evidence of the assessed outcomes in the three comparisons was very low. Data on our prespecified outcomes were either missing or not reported. Microwave coagulation plus conventional transarterial chemoembolisation (TACE) versus conventional TACE alone One trial, conducted in China, randomised 50 participants (mean age 60 years, 76% males) with liver metastases from various primary sites. Authors reported that the follow-up period was at least one month. The trial reported adverse events or complications in the experimental group only and for tumour response measures. There were no dropouts in the trial. The trial did not report on any other outcomes. Microwave ablation versus conventional surgery One trial, conducted in Japan, randomised 40 participants (mean age 61 years, 53% males) with multiple liver metastases of colorectal cancer. Ten participants were excluded after randomisation (six from the experimental and four from the control group); thus, the trial analyses included 30 participants. Follow-up was three years. The reported number of deaths from all causes was 9/14 included participants in the microwave group versus 12/16 included participants in the conventional surgery group. The mean overall survival was 27 months in the microwave ablation and 25 months in the conventional surgery group. The three-year overall survival was 14% with microwave ablation and 23% with conventional surgery, resulting in an HR of 0.91 (95% CI 0.39 to 2.15). The reported frequency of adverse events or complications was comparable between the two groups, except for the required blood transfusion, which was more common in the conventional surgery group. There was no intervention-related mortality. Disease-free survival was 11.3 months in the microwave ablationgroup and 13.3 months in the conventional surgery group. The trial did not report on HRQoL. Microwave ablation versus radiofrequency ablation One trial, conducted in Germany, randomised 50 participants (mean age 62.8 years, 46% males) who were followed for 24 months. Two-year mortality showed an RR of 0.62 (95% CI 0.26 to 1.47). The trial reported that, by two years, 76.9% of participants in the microwave ablationgroup and 62.5% of participants in the radiofrequency ablation group survived (HR 0.63, 95% CI 0.23 to 1.73). The trial reported no deaths or major complications during the procedures in either group. There were two minor complications only in the radiofrequency ablation group (RR 0.19, 95% CI 0.01 to 3.67). The trial reported technical efficacy in 100% of procedures in both groups. Distant recurrence was reported for 10 participants in the microwave ablation group and nine participants in the radiofrequency ablation group (RR 1.03, 95% CI 0.50 to 2.08). No participant in the microwave ablation group demonstrated local progression at 12 months, while that occurred in two participants in the radiofrequency ablation group (RR 0.19, 95% CI 0.01 to 3.67). The trial did not report on HRQoL. One trial reported partial support by Medicor (MMS Medicor Medical Supplies GmbH, Kerpen, Germany) for statistical analysis. The remaining two trials did not provide information on funding. We identified four ongoing trials.

AUTHORS' CONCLUSIONS

The evidence is very uncertain about the effect of microwave ablation in addition to conventional TACE compared with conventional TACE alone on adverse events or complications. We do not know if microwave ablation compared with conventional surgery may have little to no effect on all-cause mortality. We do not know the effect of microwave ablation compared with radiofrequency ablation on all-cause mortality and adverse events or complications either. Data on all-cause mortality and time to mortality, HRQoL, adverse events or complications, cancer mortality, disease-free survival, failure to clear liver metastases, recurrence of liver metastases, time to progression of liver metastases, and tumour response measures were either insufficient or were lacking. In light of the current inconclusive evidence and the substantial gaps in data, the pursuit of additional good-quality, large randomised clinical trials is not only justified but also essential to elucidate the efficacy and comparative benefits of microwave ablation in relation to various interventions for liver metastases. The current version of the review, in comparison to the previous one, incorporates two new trials in two additional microwave ablation comparisons: 1. in addition to conventional TACE versus conventional TACE alone and 2. versus radiofrequency ablation.

A multicenter case-controlled study on laparoscopic hepatectomy versus microwave ablation as first-line therapy for 3-5 cm hepatocellular carcinoma in patients aged 60 and older

BACKGROUND

There is currently a lack of convincing evidence for microwave ablation (MWA) and laparoscopic liver resection (LLR) for patients ≥60 years old with 3-5 cm hepatocellular carcinoma.

MATERIALS AND METHODS

Patients were divided into three cohorts based on restricted cubic spline analysis: 60-64, 65-72, and ≥73 years. Propensity score matching (PSM) was performed to balance the baseline variables in a 1:1 ratio. Overall survival (OS) and disease-free survival (DFS) were assessed, followed by a comparison of complications, hospitalization, and cost.

RESULTS

Among 672 patients, the median age was 66 (IQR 62-71) years. After PSM, two groups of 210 patients each were selected. During the 36.0 (20.4-52.4) month follow-up period, the 1-year, 3-year, and 5-year OS rates in the MWA group were 97.6, 80.9, and 65.3% and 95.5, 78.7, and 60.4% in the LLR group (HR 0.98, P =0.900). The corresponding DFS rates were 78.6, 49.6, and 37.5% and 82.8, 67.8, and 52.9% (HR 1.52, P =0.007). The 60-64 age cohort involved 176 patients, with no a significant difference in OS between the MWA and LLR groups (HR 1.25, P =0.370), MWA was associated with a higher recurrence rate (HR 1.94, P =0.004). A total of 146 patients were matched in the 65-72 age cohort, with no significant differences in OS and DFS between the two groups (OS (HR 1.04, P =0.900), DFS (HR 1.56, P =0.110)). In 76 patients aged ≥73 years after PSM, MWA provided better OS for patients (HR 0.27, P =0.015), and there were no significant differences in DFS between the two groups (HR 1.41, P =0.380). Taken together, for patients older than 65 years, the recurrence rate of MWA was comparable with LLR. Safety analysis indicated that LLR was associated with more postoperative bleeding ( P =0.032) and hypoproteinemia ( P =0.024).

CONCLUSIONS

MWA was comparable to LLR in patients aged 65 years and older. MWA could be an alternative for the oldest old or the ill patients who cannot afford LLR, while LLR is still the first option of treatments for early-stage 3-5 cm hepatocellular carcinoma in capable elderly's.

Microwave ablation versus liver resection for primary intrahepatic cholangiocarcinoma within Milan criteria: a long-term multicenter cohort study

Background

Ablation has been recommended by worldwide guidelines as first-line treatment for hepatocellular carcinoma (HCC), while evidence regarding its efficacy for primary intrahepatic cholangiocarcinoma (iCCA) is lacking. We aimed to study the efficacy of ablation in treating iCCA by comparing its prognosis with surgery.

Methods

In this real-world multicenter cohort study from January 2009 to June 2022, 10,441 iCCA patients from ten tertiary hospitals were identified. Patients who underwent curative-intent microwave ablation (MWA) or liver resection (LR) for tumors within Milan criteria were included. One-to-many propensity score matching (PSM) at variable ratios (1:n ≤4) was used to balance baseline characteristics. Mediation analysis was applied to identify potential mediators of the survival difference.

Findings

944 patients were finally enrolled in this study, with 221 undergoing MWA and 723 undergoing LR. After PSM, 203 patients in the MWA group were matched with 588 patients in the LR group. The median follow-up time was 4.7 years. Compared with LR, MWA demonstrated similar overall survival (5-year 44.8% versus 40.4%; HR 0.96, 95% CI 0.71-1.29, P = .761). There was an improvement in the 5-year disease-free survival rate for MWA from 17.1% during the period of 2009-2016 to 37.3% during 2017-2022, becoming comparable to the 40.8% of LR (P = .129). The proportion of ablative margins ≥5 mm increased from 25% to 61% over the two periods, while this proportion of surgical margins was 62% and 77%, respectively. 34.5% of DFS disparity can be explained by the mediation effect of margins (P < .0001). Similar DFS was observed when both ablative and surgical margins exceeded 5 mm (HR 0.83, 95% CI 0.52-1.32, P = .41).

Interpretation

MWA may be considered as a viable alternative to LR for iCCA within Milan criteria when an adequate margin can be obtained.

Funding

National Natural Science Foundation of China.

Simulation of Image-Guided Microwave Ablation Therapy Using a Digital Twin Computational Model

Emerging computational tools such as healthcare digital twin modeling are enabling the creation of patient-specific surgical planning, including microwave ablation to treat primary and secondary liver cancers. Healthcare digital twins (DTs) are anatomically one-to-one biophysical models constructed from structural, functional, and biomarker-based imaging data to simulate patient-specific therapies and guide clinical decision-making. In microwave ablation (MWA), tissue-specific factors including tissue perfusion, hepatic steatosis, and fibrosis affect therapeutic extent, but current thermal dosing guidelines do not account for these parameters. This study establishes an MR imaging framework to construct three-dimensional biophysical digital twins to predict ablation delivery in livers with 5 levels of fat content in the presence of a tumor. Four microwave antenna placement strategies were considered, and simulated microwave ablations were then performed using 915 MHz and 2450 MHz antennae in Tumor Naïve DTs (control), and Tumor Informed DTs at five grades of steatosis. Across the range of fatty liver steatosis grades, fat content was found to significantly increase ablation volumes by approximately 29-l42% in the Tumor Naïve and 55-60% in the Tumor Informed DTs in 915 MHz and 2450 MHz antenna simulations. The presence of tumor did not significantly affect ablation volumes within the same steatosis grade in 915 MHz simulations, but did significantly increase ablation volumes within mild-, moderate-, and high-fat steatosis grades in 2450 MHz simulations. An analysis of signed distance to agreement for placement strategies suggests that accounting for patient-specific tumor tissue properties significantly impacts ablation forecasting for the preoperative evaluation of ablation zone coverage.

Outpatient percutaneous image-guided microwave ablation with monitored anesthesia care: An exploratory study

PURPOSE

To evaluate the feasibility, safety, and periprocedural perception of pain for a combination approach of moderate and deep sedation for image-guided percutaneous microwave ablation of both primary and secondary malignant lesions.

METHODS

This was a retrospective study of 33 image-guided percutaneous microwave ablation procedures performed on 33 patients in an outpatient-based interventional radiology center. We used a combination of midazolam, fentanyl, propofol, and/or ketamine to achieve mild to moderate sedation for the procedure, and also to achieve deeper sedation as needed for the ablation portion.

RESULTS

Technical success was achieved in all image-guided percutaneous microwave ablation procedures. Mean procedural time was 49.4 min. There were no major complications. Intraprocedural pain was absent in all patients. All 33 patients were deemed fit for discharge within 30 min following the procedure.

CONCLUSION

The combination approach of moderate and deep sedation for anesthesia during image-guided percutaneous microwave ablation is an advantageous option. This approach has a strong safety profile, good technical success, short procedure times, low levels of intraprocedural and post-procedural pain, and short recovery from anesthesia.

Learning curve of microwave ablation for liver cancers

PURPOSE

To evaluate MWA efficacy and safety by cumulative MWA volume and interventional experience.

METHOD

3113 primary liver cancers treated by 7 operators between 2006 and 2018 were studied. Conditional logistic regression was used to estimate within-operators effects of increasing cumulative MWA volume per year on major complication, technical efficacy (TE) and local tumor progression (LTP) rates were adjusted for treatment-level characteristics. Changes were also evaluated by subgroups of tumor size and location.

RESULTS

Lower severe complication rate was detected only in higher MWA volume (HR: 0.31, P = 0.02)). TE rates increased with the increase of MWA volume ((100-150 procedures (HR: 0.33, P = 0.00); 150-200 procedures (HR: 0.08, P = 0.00)) per year. Similar results were found in subgroup analysis of interventional experience (5 to < 10 years (HR: 0.10, P = 0.00). MWA volume per year larger than 150 cases could reduce the major complication rate for tumors smaller than 5 cm (HR: 0.21, P = 0.03) and tumors in higher risk location (HR: 0.18, P = 0.03). The increase of MWA volume per year could significantly increase the TE rate in all tumor size, expect for tumors in high-risk location (100-150 procedures (HR:1.12, P = 0.84), 150-200 procedures (HR: 0.14, P = 0.08)).

CONCLUSIONS

Early and intensive performance of MWA procedures would reduce major complication rates regardless of tumor size and tumor location, but could not improve TE rate in high-risk locations.

Clinical guidelines for microwave ablation of spinal metastases

Spinal metastases are the most common source of morbidity in patients with cancer. Recently, microwave ablation has produced satisfactory results in the management of spinal metastases. However, there is still controversy in terms of clinical treatment, such as indication, power, time, and temperature. To standardize the application of microwave ablation technology and reduce the risk of surgical-related complications in spinal metastases, in this report, we aimed to summarize the current evidence and clinical experience of microwave ablation and developed a clinical guideline, initiated by the Musculoskeletal Tumor Group of the Committee for Minimally Invasive Therapy in Oncology of the Chinese Anti-Cancer Association. The Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach was used in to rate the quality of evidence and the strength of recommendations, and the Reporting Items for Practice Guidelines in Healthcare (RIGHT) checklist was strictly followed to report the guideline. Finally, 15 evidence-based recommendations were formulated based on the 15 most concerned clinical questions among orthopedic surgeons, oncologists, and interventional radiologists in China. This guideline aims to promote the science-based normalization of microwave ablation for the treatment of spinal metastases.

Microwave ablation combined with apatinib and camrelizumab in patients with advanced hepatocellular carcinoma: A single-arm, preliminary study

PURPOSE

The aim of this study was to assess the safety and efficacy of microwave ablation combined with apatinib [vascular endothelial growth factor receptor-2 (VEGFR-2) inhibitor] and camrelizumab [anti-programmed death-1 (PD-1) antibody] in patients with advanced hepatocellular carcinoma (HCC).

PATIENTS AND METHODS

Patients (age, >18 years) with histologically confirmed HCC and refractory to at least the standard first-line therapy were enrolled from 2 September 2018 to 17 January 2022. They first received ultrasound-guided subtotal microwave ablation. Then, beginning at 7-14 days after ablation, they were given apatinib (250 mg once daily) and camrelizumab (200 mg once every 2 weeks) until unacceptable toxicity or disease progression or death. The coprimary end points were progression-free survival (PFS) and overall survival (OS).

RESULTS

Fourteen HCC patients with Barcelona Clinic of Liver Cancer (BCLC) B and C stages were retrospectively enrolled. At data cutoff, follow-up period ranged from 3.8 to 41.3 months (median, 17.4 months), and the median (95% confidence interval) duration of exposure (DE) was 6.4 (4.0-8.9) months. The PFS and OS were 10.8 (0-23.5) months and 19.3 (2.4-36.2) months, respectively. Three (21.4%) patients achieved a confirmed complete response (CR). Confirmed partial response (PR), stable disease (SD), and progression of disease (PD) were achieved in four (28.6%), four (28.6%), and three (21.4%) patients, respectively. The objective response rate (ORR) and disease control rate (DCR) were 50.0% (20.0%-80.0%) and 78.6% (54.0%-100%), respectively. The serious treatment-related adverse events included one (7.1%) case with reactive capillary hemangiomas (grade 4), one (7.1%) with hypertension (grade 3), two (14.3%) with elevated transaminase and bilirubin (grade 4), one (7.1%) with platelet count decrease (grade 4), one (7.1%) with hepatic failure (grade 4), and two (14.3%) with gastrointestinal bleeding (grades 3 and 4).

CONCLUSIONS

Microwave ablation combined with apatinib and camrelizumab treatment in advanced HCC patients demonstrated intriguing clinical activity and resulted in durable antitumor responses and significantly improved PFS and OS. The combination therapy is well tolerated, enabling further clinical studies.

Hepatic resection versus microwave ablation for the treatment of early hepatocellular carcinoma: a comparative analysis of treatment outcomes and survival predictors

Introduction

Liver resection and local ablation are the two primary curative treatments for early-stage hepatocellular carcinoma (HCC). Microwave ablation (MWA) shows promising performance in terms of early tumor response, recurrence, and survival. This study aims to determine whether MWA would be comparable to liver resection in treating early-stage HCC.

Methods

This study included patients with hepatitis C-related HCC attending the multidisciplinary HCC clinic, Kasr Al-Ainy Hospital (March 2018 to September 2020). We included adults with early-stage HCC (BCLC stages 0-A). We studied patients and tumor characteristics, HCC treatment response, recurrence, and overall survival.

Results

Thirty-one patients were treated with liver resection and 41 patients were treated with MWA, including 4 patients who received intraoperative MWA. By the end of the study, 21 patients (28.77%) died. Patients who underwent MWA were younger compared to the hepatectomy group with lower baseline AFP (21 (6.7–54) versus 77 (31.3–136.0), respectively, (P value 0.024) and tumor size (2.78 (0.87) cm versus 3.77 (0.97) cm, respectively, (P value < 0.001). We found no differences between the studied groups in terms of treatment response, post-treatment decompensation, recurrence, or overall survival. One-year survival probability in the MWA and resection groups was 75.5% and 76.3% respectively. Post-procedure hepatic decompensation was the only independent predictor of lower survival by multivariate logistic regression analysis (OR 37.74, 95%CI 6.251–227.87, P value < 0.001) after adjusting for age, AFP, and tumor size.

Conclusion

Liver resection and MWA showed similar satisfactory results in the treatment of early-stage HCC, in terms of treatment response, recurrence, and overall survival.

Effects of microwave ablation on serum Golgi protein 73 in patients with primary liver cancer

BACKGROUND

Microwave ablation (MWA) is an effective treatment option for patients with primary liver cancer. However, it has been reported that the MWA procedure induces a hepatic inflammatory response and injury, which may negatively affect the efficacy of MWA. As such, the discovery of reliable markers to monitor the patient’s response to MWA is needed. Golgi protein 73 (GP73) has been shown to be associated with chronic liver disease. To date, the potential value of serum GP73 in the dynamic monitoring during MWA of liver cancer remains unclear.

AIM

To examine the effects of MWA on the serum levels of GP73 in patients with primary liver cancer.

METHODS

A total of 150 primary liver cancer patients with a single small lesion (≤ 3 cm in diameter) were retrospectively enrolled spanning the period between January 2016 and October 2018. All of the patients received MWA for the treatment of primary liver cancer. Serum GP73, alpha-fetoprotein (AFP), and widely used liver biochemical indicators [serum albumin, total bilirubin (TBIL), alanine aminotransferase (ALT), and aspartate aminotransferase (AST)] were compared before MWA and at different time points, including 1, 2, and 4 wk following the ablation procedure.

RESULTS

Complete tumor ablation was achieved in 95.33% of the patients at 1 mo after MWA. The 1-, 2-, and 3-year disease-free survival rates were 74.67%, 59.33%, and 54.00%, respectively. The serum AFP levels were significantly decreased at 1, 2, and 4 wk after MWA; they returned to the normal range at 12 wk after MWA; and they remained stable thereafter during follow-up in those cases without recurrence. In contrast, the serum GP73 levels were significantly increased at 1 and 2 wk after MWA. The serum GP73 levels reached the peak at 2 wk after MWA, started to decline after hepatoprotective treatment with glycyrrhizin and reduced glutathione, and returned to the pretreatment levels at 12 and 24 wk after MWA. Notably, the changes of serum GP73 in response to MWA were similar to those of TBIL, ALT, and AST.

CONCLUSION

Serum GP73 is markedly increased in response to MWA of liver cancer. Thus, serum GP73 holds potential as a marker to monitor MWA-induced inflammatory liver injury in need of amelioration.

Efficacy and safety of microwave ablation and radiofrequency ablation in the treatment of hepatocellular carcinoma: A systematic review and meta-analysis

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors. Surgical resection is often only possible in the early stages of HCC and among those with limited cirrhosis. Radiofrequency ablation and Microwave ablation are 2 main types of percutaneous thermal ablation for the treatment of HCC. The efficacy and safety between these 2 therapy methods are still under a debate.

OBJECTIVE

To compare the efficacy and safety of Radiofrequency ablation and Microwave ablation in treating HCC.

METHODS

PubMed, EMBASE, the Cochrane databases and Web of Science were systematically searched. We included randomized controlled trials and cohort studies comparing the efficacy and safety of Radiofrequency ablation and Microwave ablation in HCC patients. Outcome measures on local tumor progression, complete ablation, disease-free survival, overall survival, or major complications were compared between the 2 groups. The random effect model was used when there was significant heterogeneity between studies, otherwise the fixed effect model was used.

RESULTS

A total of 33 studies, involving a total of 4589 patients were identified, which included studies comprised 7 RCTs, 24 retrospective observational trials, and 2 prospective observational trial. Microwave ablation had a lower local tumor progression than Radiofrequency ablation in cohort studies (OR = 0.78, 95% CI 0.64-0.96, P = .02). Complete ablation rate of Microwave ablation was higher than that of Radiofrequency ablation in cohort studies (OR = 1.54, 95% CI 1.05-2.25, P = .03). There was no significant difference in overall survival and disease-free survival between the 2 groups. Meta-analysis showed that there was no significant difference in the main complications between Microwave ablation and Radiofrequency ablation.

CONCLUSIONS

Microwave ablation has higher complete ablation and lower local tumor progression than Radiofrequency ablation in the ablation treatment of HCC nodules. There was no significant difference in overall survival between the 2 therapy methods.

Microwave ablation versus laparoscopic resection as first-line therapy for solitary 3-5-cm HCC

BACKGROUND AND AIMS

The study objective was to compare the effectiveness of microwave ablation (MWA) and laparoscopic liver resection (LLR) on solitary 3-5-cm HCC over time.

APPROACH AND RESULTS

From 2008 to 2019, 1289 patients from 12 hospitals were enrolled in this retrospective study. Diagnosis of all lesions were based on histopathology. Propensity score matching was used to balance all baseline variables between the two groups in 2008-2019 (n = 335 in each group) and 2014-2019 (n = 257 in each group) cohorts, respectively. For cohort 2008-2019, during a median follow-up of 35.8 months, there were no differences in overall survival (OS) between MWA and LLR (HR: 0.88, 95% CI 0.65-1.19, p = 0.420), and MWA was inferior to LLR regarding disease-free survival (DFS) (HR 1.36, 95% CI 1.05-1.75, p = 0.017). For cohort 2014-2019, there was comparable OS (HR 0.85, 95% CI 0.56-1.30, p = 0.460) and approached statistical significance for DFS (HR 1.33, 95% CI 0.98-1.82, p = 0.071) between MWA and LLR. Subgroup analyses showed comparable OS in 3.1-4.0-cm HCCs (HR 0.88, 95% CI 0.53-1.47, p = 0.630) and 4.1-5.0-cm HCCs (HR 0.77, 95% CI 0.37-1.60, p = 0.483) between two modalities. For both cohorts, MWA shared comparable major complications (both p > 0.05), shorter hospitalization, and lower cost to LLR (all p < 0.001).

CONCLUSIONS

MWA might be a first-line alternative to LLR for solitary 3-5-cm HCC in selected patients with technical advances, especially for patients unsuitable for LLR.

Physical & Chemical Microwave Ablation (MWA) Enabled by Nonionic MWA Nanosensitizers Repress Incomplete MWA-Arised Liver Tumor Recurrence

Ionic liquid (IL)-loaded or metal ions-enriched nanoparticles have been witnessed to assist microwave ablation (MWA) and heighten heat utilization for tumor treatment, which, however, inevitably brings about cell dys-homeostasis and severely endangers normal cells or tissues. In this report, a nonionic MWA sensitizer that encapsulates ethyl formate (EF) and doxorubicin (DOX) in liposomes (EF-DOX-Lips) was constructed to reinforce MWA and combined therapy against incomplete MWA-induced tumor recurrence. EF in EF-DOX-Lips as the nonionic liquid can perform like IL to accelerate energy transformation from electromagnetic energy to heat for strengthening MWA. More significantly, EF metabolite, that is, ethanol, also enables chemical ablation, which further enhances MWA. As well, the EF gasification-enhanced lipid rupture and cavitation can promote DOX delivery into a liver tumor for magnifying MWA & chemotherapy combined therapy. By virtue of these contributions, this nonionic MWA nanosensitizer exerts robust antitumor effects to inhibit tumor proliferation and angiogenesis for repressing tumor growth and recurrence or metastasis via downregulating the Epha2 gene and unconventional PI3K/Akt & MAPK signal pathways that the incomplete MWA activated, which provides an avenue to elevate an MWA-based antitumor outcome.

Cause Analysis and Diagnosis and Treatment of Intestinal Fistulas After Ultrasound-Guided Microwave Ablation of Abdominopelvic Lesions

Objective: To determine the cause and high-risk factors for the development of intestinal fistulas (IFs) after ultrasound-guided microwave ablation (MA) of abdominopelvic lesions, and to identify effective prophylactic and therapeutic actions. Methods: Clinical data were collected from patients with an IF after ultrasound-guided MA of abdominopelvic lesions in our hospital from January 1, 2010 to December 31, 2018. The cause, diagnosis, and treatment of IFs in these patients were analyzed. Results: Among 8,969 patients who underwent ultrasound-guided MA of abdominopelvic lesions, eight patients developed IF after MA, Seven patients were discharged after being cured and one died. Conclusion: Abdominopelvic lesions are close to the intestines, so histories of surgery, radiotherapy, and abdominopelvic infection are high-risk factors for IF development after MA of these lesions. Surgical treatment should be provided as soon as an IF is identified.

Review of clinical tumor ablation advance in Asia

Tumor ablation has been widely applied in Asia, accounting for 44.65% of clinical studies worldwide. We reviewed 5853 clinical studies to provide insight on the advance of tumor ablation in Asia chronologically and geographically among different techniques and organs. Since 1998, tumor ablation application has dramatically evolved in Asia. All kinds of ablation techniques, including percutaneous ethanol injection (PEI), radiofrequency ablation (RFA), microwave ablation (MWA), laser ablation (LA), cryoablation (CA), high-intensity focused ultrasound (HIFU), and irreversible electroporation (IRE), have been applied, with the first application of PEI and the most popular application of RFA. Twenty-five countries and one district in Asia have applied tumor ablation in various organs, including liver, lung, uterus, thyroid, kidney, pancreas, bone, prostate, breast, adrenal gland, lymph node parathyroid, esophagus, etc. Due to the high incidence of tumors as well as advanced economy and technology, East Asia accounted for 93.87% of studies, led by China (45.00%), Japan (32.72%), South Korea (12.10%), and Taiwan (4.03%). With the enrichment of evidence from large-scale multicenter and randomized control studies, China and South Korea have issued several guidelines on tumor ablation for liver, lung, and thyroid, which provided recommendations for global standardization of tumor ablation techniques. Therefore, Asia has made active contribution to global tumor ablation therapy.KeypointsKey point 1: Asia accounted for 44.65% of clinical studies worldwide on tumor ablation.Key point 2: Twenty-five countries and one district in Asia have used tumor ablation in various organs, and East Asia accounted for 93.87% of studies, led by China (45.00%), Japan (32.72%), South Korea (12.10%), and Taiwan (4.03%).Key point 3: China and South Korea have issued several guidelines on tumor ablation for liver, lung, and thyroid, which provided recommendations for global standardization of tumor ablation techniques.

Microwave ablation vs. surgical resection for treatment naïve hepatocellular carcinoma within the Milan criteria: a follow-up of at least 5 years

OBJECTIVE

Thermal ablation poses challenges in the surgical resection (SR) of small hepatocellular carcinoma (HCC), and its therapeutic outcomes for larger lesions remain debated.

METHODS

This retrospective study evaluated 729 patients with HCC meeting the Milan criteria, who were treated with curative SR or microwave ablation (MWA) between 2008 and 2014. Overall survival (OS), cancer-specific survival (CSS), disease-free survival (DFS), and local tumor progression (LTP) were compared after propensity score matching (PSM). Co-variates associated with OS, CSS, LTP, and DFS were identified. The risk of death and tumor progression were compared.

RESULTS

During the median follow-up of 78.6 months, 253 patients were included in each group after PSM. For tumors ≤ 3.0 cm and 3.1-4.0 cm, MWA achieved comparable results in terms of OS, CSS, DFS, and LTP. For tumors 4.1-5.0 cm, MWA had lower OS, CSS, and DFS rates (all P < 0.05) than SR. Higher LTP rates were observed in the MWA group for tumors 4.1-5.0 cm, although the difference was not significant (P = 0.18). Complication rates (P = 0.41) were similar, but MWA led to less estimated blood loss (P < 0.01) and shorter postoperative hospitalization times (P < 0.01).

CONCLUSIONS

MWA achieved comparable long-term oncologic outcomes with SR for ≤ 4 cm HCC, with lower complication rates and faster recovery.

Differential Imaging of Liver Tumors before and after Microwave Ablation with Electrode Displacement Elastography

Liver cancer is a leading cause of cancer-related deaths; however, primary treatment options such as surgical resection and liver transplant may not be viable for many patients. Minimally invasive image-guided microwave ablation (MWA) provides a locally effective treatment option for these patients with an impact comparable to that of surgery for both cancer-specific and overall survival. MWA efficacy is correlated with accurate image guidance; however, conventional modalities such as B-mode ultrasound and computed tomography have limitations. Alternatively, ultrasound elastography has been used to demarcate post-ablation zones, yet has limitations for pre-ablation visualization because of variability in strain contrast between cancer types. This study attempted to characterize both pre-ablation tumors and post-ablation zones using electrode displacement elastography (EDE) for 13 patients with hepatocellular carcinoma or liver metastasis. Typically, MWA ablation margins of 0.5-1.0 cm are desired, which are strongly correlated with treatment efficacy. Our results revealed an average estimated ablation margin inner quartile range of 0.54-1.21 cm with a median value of 0.84 cm. These treatment margins lie within or above the targeted ablative margin, indicating the potential to use EDE for differentiating index tumors and ablated zones during clinical ablations. We also obtained a high correlation between corresponding segmented cross-sectional areas from contrast-enhanced computed tomography, the current clinical gold standard, when compared with EDE strain images, with r2 values of 0.97 and 0.98 for pre- and post-ablation regions.

Ultrasound-guided Microwave Ablation in the Management of Symptomatic Uterine Myomas: A Systematic Review and Meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to evaluate the clinical effects and safety of ultrasound-guided microwave ablation (MWA) for the treatment of symptomatic uterine myomas.

DATA SOURCES

We searched PubMed, Web of Science Core Collection, Cochrane Library, Embase, Scopus, and Google Scholar for studies from January 2000 to January 2021.

METHODS OF STUDY SELECTION

We included all studies that reported the clinical outcomes of ultrasound-guided MWA in women with symptomatic uterine myomas. Two researchers conducted the study selection according to the screening criteria.

TABULATION, INTEGRATION, AND RESULTS

We evaluated the risk of bias and evidence quality using the Newcastle-Ottawa scale. Two researchers independently extracted information from the included studies. We extracted the standardized mean difference (SMD) and pooled proportion with a 95% confidence interval (CI) for the outcome measures of interest. A total of 10 studies representing 671 patients were included. The Uterine Fibroid Symptom and Quality of Life (UFS-QoL) questionnaire was used to assess the clinical effects. Compared with baseline, the UFS scores decreased significantly (SMD 3.37; 95% CI, 2.27-4.47; p <.001; reduction rate 65.9%), QoL scores increased significantly (SMD -3.12; 95% CI, -3.93 to -2.30; p <.001; rate of increase 72.0%), and hemoglobin concentration increased significantly (SMD -2.13; 95% CI, -3.44 to -0.81; p = .002; rate of increase 30.3%) at follow-up. The mean operation time was 34.48 minutes (95% CI, 22.82-46.13; p <.001). The rate of reduction in myoma volume after MWA was 85.3% (95% CI, 82.7%-88.0%, p <.001). No major adverse event was reported, and the incidence of minor adverse events was 21.1% (95% CI, 15.1%-27.0%, p <.001).

CONCLUSION

Ultrasound-guided MWA is an effective and safe minimally invasive therapy for symptomatic uterine myomas.

Percutaneous microwave ablation of renal cell carcinoma: practice guidelines of the ultrasound committee of Chinese medical association, interventional oncology committee of Chinese research hospital association

Imaging-guided percutaneous microwave ablation (MWA) with high thermal efficiency comprises rapid, successful management of small renal cell carcinomas (RCCs) in selected patients. Ultrasound Committee of Chinese Medical Association, Interventional Oncology Committee of Chinese Research Hospital Association developed evidence-based guidelines for MWA of RCCs after systematically reviewing the 1969-2019 literature. Systematic reviews, meta-analyses, randomized controlled trials, cohort, and case-control studies reporting MWA of RCCs were included and levels of evidence assessed. Altogether, 146 articles were identified, of which 35 reported percutaneous MWA for T1a RCCs and 5 articles for T1b RCCs. Guidelines were established based on indications, techniques, safety, and effectiveness of MWA for RCCs, with the goal of standardizing imaging-guided percutaneous MWA treatment of RCCs. Key points Microwave ablation is recommended for managing small renal cell carcinoma in selected patients. Imaging protocols are tailored based on the procedural plan, guidance, and evaluation. Patient's selection evaluation, updated technique information, clinical efficacy, and complications are recommended to standardize management. A joint task force (multidisciplinary team) summarized the key elements of the standardized report.

Locoregional Combined With Systemic Therapies for Advanced Hepatocellular Carcinoma: An Inevitable Trend of Rapid Development

Despite the application of antiviral drugs and improved surveillance tools, the number of patients diagnosed with hepatocellular carcinoma (HCC) at an advanced stage and with a dismal prognosis is still on the rise. Systemic treatment with multiple multitargeted tyrosine kinase inhibitors (TKIs), such as sorafenib, has been a widely utilized approach for a decade. In addition, the use of a combination of TKIs with other types of compounds, including immune checkpoint inhibitors (ICIs) and antiangiogenic inhibitors, has shown efficacy in treating advanced HCC. However, the presence of intolerable adverse events, low disease response and control rates, and relative short overall survival of such combinatory therapies makes novel or optimized therapies for advance HCC urgently needed. Locoregional therapy (transarterial chemoembolization, and thermal ablation) can destroy primary tumors and decrease tumor burden and is widely used for HCC management. This type of treatment modality can result in local hypoxia and increased vascular permeability, inducing immunogenic effects by releasing tumor antigens from dying cancer cells and producing damage-associated molecular patterns that facilitate antiangiogenic therapy and antitumor immunity. The combination of systemic and locoregional therapies may further produce synergistic effects without overlapping toxicity that can improve prognoses for advanced HCC. In preliminary studies, several combinations of therapeutic modes exhibited promising levels of safety, feasibility, and antitumor effects in a clinical setting and have, thus, garnered much attention. This review aims to provide a comprehensive, up-to-date overview of the underlying mechanisms of combined systemic and locoregional therapies in the treatment of advanced HCC, commenting on both their current status and future direction.

Percutaneous Microwave Ablation of Liver Lesions: Differences on the Sphericity Index of the Ablation Zone between Cirrhotic and Healthy Liver Parenchyma

To compare different parameters of the sphericity index of the ablation zone following microwave ablation (MWA) on cirrhotic- and healthy-liver parenchyma in a series of patients treated with the same MWA system. Institutional database research identified 46 patients (77 lesions) who underwent MWA. “Cirrhotic liver group” (CLG) included 35 hepatocellular carcinoma lesions; “healthy liver group” (HLG) included 42 metastatic lesions. The long axis (LAD), short axis 1 (SAD-1) and 2 (SAD-2), the mean SAD-1 and SAD-2 (mSAD) diameter (in mm) and the mean sphericity (mSPH) index of the ablation zones were evaluated for each treated lesion in both groups from baseline to follow-up. A mixed model analysis of variance reported significant main effect of group on SAD-1 (p = 0.023), SAD-2 (p = 0.010) and mSAD (p = 0.010), with HLG showing lower values compared to CLG. No differences were detected on the LAD (p_FDR = 0.089; d = 0.45), and mSPH (p_FDR = 0.148, d = 0.40) between the two groups. However, a significant main effect of time was found on LAD (p < 0.001), SAD-1 (p < 0.001), SAD-2 (p < 0.001) and mSAD (p < 0.001), with decreased values in all indices at follow-up compared to baseline. A significant group by time interaction was observed on mSPH (p = 0.044); HLG had significantly lower mSPH at follow-up where CLG did not show any significant change. Our findings indicate that although in cirrhotic liver short axis diameter of the MWA zone seems to be significantly longer, this has no effect on the sphericity index which showed no significant difference between cirrhotic vs. healthy liver lesions. On the contrary, on one month follow-up ablation zones tend to become significant more ellipsoid in healthy whilst remains stable in cirrhotic liver.

Advanced Techniques in the Percutaneous Ablation of Liver Tumours

Percutaneous ablation is an accepted treatment modality for primary hepatocellular carcinoma (HCC) and liver metastases. The goal of curative ablation is to cause the necrosis of all tumour cells with an adequate margin, akin to surgical resection, while minimising local damage to non-target tissue. Aside from the ablative modality, the proceduralist must decide the most appropriate imaging modality for visualising the tumour and monitoring the ablation zone. The proceduralist may also employ protective measures to minimise injury to non-target organs. This review article discusses the important considerations an interventionalist needs to consider when performing the percutaneous ablation of liver tumours. It covers the different ablative modalities, image guidance, and protective techniques, with an emphasis on new and advanced ablative modalities and adjunctive techniques to optimise results and achieve satisfactory ablation margins.

How to Treat Hepatocellular Carcinoma in Elderly Patients

Hepatocellular carcinoma (HCC) is the primary tumour of the liver with the greatest incidence, particularly in the elderly. Additionally, improvements in the treatments for chronic liver diseases have increased the number of elderly patients who might be affected by HCC. Little evidence exists regarding HCC in old patients, and the elderly are still underrepresented and undertreated in clinical trials. In fact, this population represents a complex subgroup of patients who are hard to manage, especially due to the presence of multiple comorbidities. Therefore, the choice of treatment is mainly decided by the physician in the clinical practice, who often tend not to treat elderly patients in order to avoid the possibility of adverse events, which may alter their unstable equilibrium. In this context, the clarification of the optimal treatment strategy for elderly patients affected by HCC has become an urgent necessity. The aim of this review is to provide an overview of the available data regarding the treatment of HCC in elderly patients, starting from the definition of "elderly" and the geriatric assessment and scales. We explain the possible treatment choices according to the Barcelona Clinic Liver Cancer (BCLC) scale and their feasibility in the elderly population.

Percutaneous microwave ablation applications for liver tumors: recommendations for COVID-19 patients

Microwave ablation (MWA) is an alternative locoregional therapy to surgical resection of solid tumors in the treatment of malignancies, and is widely used for hepatic tumors. It has a slightly higher overall survival (OS) rate compared to external beam radiation therapy (EBRT), and proton beam therapy (PBT), and better long-term recurrence-free OS rate compared to radiofrequency ablation (RFA). In this paper, current commercial devices, most recent noncommercial designs, and the principles behind them alongside the recently reported developments and issues of MWA are reviewed. The paper also provides microscopic insights on effects of microwave irradiation in the body. Our review shows that MWA is a safe and effective, minimally invasive method with high ablation completion rates. However, for large tumors, the completion rates slightly decrease, and recurrences increase. Thus, for large tumors we suggest using a cooled shaft antenna or multiple antenna placements. Comparisons of the two common ablation frequencies 915 MHz and 2.45 GHz have shown inconsistent results due to non-identical conditions. This review suggests that 915 MHz devices are more effective for ablating large tumors and the theory behind MWA effects corroborates this proposition. However, for small tumors or tumors adjacent to vital organs, 2.45 GHz is suggested due to its more localized ablation zone. Among the antenna designs, the double-slot antenna with a metallic choke seems to be more effective by localizing the radiation around the tip of the antenna, while also preventing backward radiation towards the skin. The review also pertains to the use of MWA in COVID-19 patients and risk factors associated with the disease. MWA should be considered for COVID-19 patients with hepatic tumors as a fast treatment with a short recovery time. As liver injury is also a risk due to COVID-19, it is recommended to apply liver function tests to monitor abnormal levels in alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin, and other liver function indicators.

Feasibility of Controlling Metastatic Osseous Pain Using Three Kinds of Image-Guided Procedures for Thermal Microwave Ablation: A Retrospective Study

Objectives

To evaluate the feasibility and safety of treating painful osseous metastases using image‐guided percutaneous thermal microwave ablation.

Methods

This is a retrospective study of patients treated from December 2016 to December 2019 in one institute. A total of 50 patients (35 men, 15 women; mean age 55.24 ± 11.03 years) with 56 osseous metastatic lesions underwent image‐guided percutaneous microwave ablation. There were 7 patients with multiple and 43 patients with single metastases. The numbers of patients with primary cancer were as follows: lung, 13; liver, 17; kidney, 10; prostate, 1; breast, 3; osteosarcoma, 1; and thyroid, 5. Seventeen patients had cancer combined with soft tissue masses. The radiological images for the ablative procedures were obtained by CT, fluoroscopy with ultrasound, and fluoroscopy alone in 16, 11, and 23 patients, respectively. Pain severity was estimated using the visual analogue scale before and after treatment (1 week, 1 month, and 3 months after treatment). Radiological evaluations were performed at baseline and 3 months after the procedure.

Results

In all patients, pain reduction occurred from the first day after treatment. Pain did not recur during the 3 months of follow up. The mean total ablation time per microwave electrode was 3.99 ± 2.48 min (range, 1–15 min). The mean power of the microwave electrode was 66.40 ± 12.08 W. The average volume of bone (load‐bearing bone, such as vertebra and acetabulum) cement after ablation was 2.82 ± 0.81 mL. There were no significant differences in visual analogue scale pain scores for different imaging techniques or ablation energies. No procedure‐related complications occurred.

Conclusion

Image‐guided percutaneous thermal microwave ablation of osseous metastases relieves pain and improves mobility. CT remains the first choice for percutaneous ablation. Fluoroscopy combined with ultrasound is effective for cases with soft tissue masses; fluoroscopy is also suitable for combination with vertebroplasty. However, further investigations are required.

(A) Microwave ablation probe. (B) Temperature probe in the vertebral body and in the vertebral pedicle (parallel to the posterior margin). (C) Metastatic tumor. The thick white line of the ablation probe tip represents the source of microwave needle emission. The orange region represents the heating range of the microwave.

The effect of tumor location on long-term results of microwave ablation for early-stage hepatocellular carcinoma

BACKGROUND

To analyze the influence of tumor location, including tumor adjacency and located segments on long-term survival outcomes for patients with solitary hepatocellular carcinoma (HCC) after microwave ablation (MWA).

METHODS

This retrospective study evaluated 850 patients. The hepatic segments where the tumor is located, tumor adjacency (important tissues adjacent to tumor) and other clinical characteristics were collected. Overall survival (OS), local tumor progression (LTP) and disease-free survival (DFS) were compared and analyzed. Influence of tumor location was evaluated by multi-models and the effect of adjacency for OS, LTP, and DFS in different segments was analyzed by stratification analysis.

RESULTS

The OS, LTP, and DFS rates were similar in different hepatic segments, so were in high risk and safe locations. In multi-models, HCC in segment 8 showed lower death rate of 43% than that in segment 2 (HR 0.57; P = 0.01) and tumors in segment 6 seemed to have lower LTP rate. Tumors in high-risk locations were risk factors for OS, LTP, and DFS compared with tumors in safe locations, but all differences were not significant in different models. The effects of tumor adjacency on survival outcomes among subgroups of segments were limited.

CONCLUSION

The tumor adjacency was not a prognostic factor of survival outcomes for patients with solitary tumors after MWA, but tumors in segment 8 seemed to better OS rate than tumors in other segments.

Role of External Beam Radiotherapy in Hepatocellular Carcinoma

External beam radiotherapy (EBRT) has improved efficacy and safety with advancements in technology and techniques. EBRT plays an important role in management of hepatocellular carcinoma (HCC). In resectable cases, EBRT serves as a bridge to transplantation or improves local control through adjuvant radiotherapy. In unresectable patients, EBRT offers high local control rates. In metastatic settings, EBRT provides effective palliation. This review presents an overview of radiotherapy treatment modalities used for HCC, current treatment guidelines for the role of EBRT in HCC, clinical outcomes between various EBRT approaches and other locoregional treatments for HCC, and the future role of EBRT for HCC.

Ultrasound-guided percutaneous microwave ablation of hepatocellular carcinoma in challenging locations: oncologic outcomes and advanced assistive technology

Purpose: To assess the oncologic outcomes of the hepatocellular carcinoma (HCC) patients in challenging locations (CLs) underwent ultrasound-guided percutaneous microwave ablation (US-PMWA) and the efficacy and safety of the advanced assistive technology (AAT).Materials and methods: Data for 489 treatment-naïve patients with HCC who met Milan criteria and subsequently underwent US-PMWA were reviewed from March 2012 to November 2016. According to the distance (<5 mm) between the tumor and surrounding structures, the patients were divided into two groups: a CL group and a non-CL group. Regarding MWA assisted by AAT, the CL group was further subdivided into two groups: an AAT group and a non-AAT group. Technique effectiveness, complications and survival outcomes (i.e., overall survival [OS] and recurrence-free survival [RFS]) were compared between CL and non-CL groups. Local tumor progression (LTP) was compared between AAT and non-AAT groups.Results: Technique effectiveness and complications in the CL group were similar to those in the non-CL group (p = .873 and p = .828, respectively). The OS and RFS in six types of CL groups were comparable with those in non-CL group (p = .131-.117) including adjacent vital structures, gallbladder, hepatic hilar regions, major vessels, diaphragm and capsule, respectively. The LTP rates in the AAT group were significantly higher than those in the non-AAT group (p = .001).Conclusions: US-PMWA assisted by AAT to treat HCC lesions in CLs was safe and effective; also, this technique had comparable success and survival outcomes with those of patients in non-CL.

Beneficial body mass index to enhance survival outcomes in patients with early-stage hepatocellular carcinoma following microwave ablation treatment

Purpose: To identify the beneficial body mass index (BMI) for patients with hepatocellular carcinoma (HCC) to achieve longer survival time following curative microwave ablation (MWA).Methods: This retrospective study evaluated 474 patients with solitary primary HCC who underwent MWA. BMI at initial admission and other characteristics were collected. The associations of the BMI with the overall survival (OS) and disease-free survival (DFS) were analyzed by Cox proportional hazards regression analysis in multiple models. A two-piecewise linear regression model was applied to examine the threshold effect of the BMI on OS and DFS by maximized log likelihood method. The threshold level was determined by using trial and error.Results: Patients with a normal BMI range achieved improved survival outcomes but similar DFS in multiple models. In the model with adjustments of the age, size, and Charlson score, patients with BMI ≤ 22.9 and ≤24.9 kg/m² exhibited a lower death rate than patients with BMI ≤18.5 kg/m² (p < 0.05). U-shaped relationships between the BMI and OS were illustrated when the BMI was set as a continuous variable. The death prevalence decreased with an increasing BMI up to the first turning point of 21.5 and increased with an increasing BMI up to the second turning point of 23.1 (p = 0.00). The threshold effect analysis indicated that no turning point was selected in the DFS results (p = 0.10).Conclusions: The beneficial BMI level for HCC patients following MWA, with a more likely favorable survival outcome, is 21.5 to 23.1 kg/m².

Ultrasound-guided percutaneous microwave ablation for hepatocellular carcinoma adjacent to large vessels: a propensity score matching analysis

PURPOSE

This study aimed to compare the efficacy and safety of ultrasound-guided percutaneous microwave ablation (MWA) for hepatocellular carcinoma (HCC) adjacent to large vessels with those far from large vessels.

METHODS

The clinical data of patients who underwent ultrasound-guided percutaneous MWA for HCC were retrospectively analyzed between January 2011 and December 2018 in Shengjing Hospital. Patients with HCC adjacent to large vessels were included in the Vessel group, the remaining patients were included in the Control group. Propensity score matching analysis was used to reduce confounding bias. The rates of complete ablation, local recurrence, recurrence-free survival (RFS), overall survival (OS) and complications were compared between the two groups.

RESULTS

A total of 134 patients with 157 nodules (size range, 0.6-3.8 cm) were enrolled in this study, 23 in the Vessel group and 111 in the Control group. A total of 21 patients in the Vessel group (91.3%) and 105 patients in the Control group (94.6%) achieved complete ablation (p = .902). Following 1:2 propensity score matching, 22 patients were included in the Vessel group and 40 patients were enrolled in the Control group. Local recurrence was observed in 2 (9.1%) patients in the Vessel group and 5 (12.5%) in the Control group (p = .86). No significant difference in local recurrence rate, RFS and OS were observed between the two groups.

CONCLUSIONS

Ultrasound-guided percutaneous MWA appears to be a safe procedure and can achieve comparable oncological efficacy for HCC abutting large vessels.

Geometrically variable three-dimensional ultrasound for mechanically assisted image-guided therapy of focal liver cancer tumors

PURPOSE

Image-guided focal ablation procedures are first-line therapy options in the treatment of liver cancer tumors that provide advantageous reductions in patient recovery times and complication rates relative to open surgery. However, extensive physician training is required and image guidance variabilities during freehand therapy applicator placement limit the sufficiency of ablation volumes and the overall potential of these procedures. We propose the use of three-dimensional ultrasound (3D US) to provide guidance and localization of therapy applicators, augmenting current ablation therapies without the need for specialized procedure suites. We have developed a novel scanning mechanism for geometrically variable 3D US images, a mechanical tracking system, and a needle applicator insertion workflow using a custom needle applicator guide for targeted image-guided procedures.

METHODS

A three-motor scanner was designed to use any commercially available US probe to generate accurate, consistent, and geometrically variable 3D US images. The designed scanner was mounted on a counterbalanced stabilizing and mechanical tracking system for determining the US probe orientation, which was assessed using optical tracking. Further exploiting the utility of the motorized scanner, an image-guidance workflow was developed that moved the probe to any identified target within an acquired 3D US image. The complete 3D US guidance system was used to perform mock targeted interventional procedures on a phantom by selecting a target in a 3D US image, navigating to the target, and performing needle insertion using a custom 3D-printed needle applicator guide. Registered postinsertion 3D US images and cone-beam computed tomography (CBCT) images were used to evaluate tip targeting errors when using the motors, tracking system, or mixed navigation approaches. Two 3D US image geometries were investigated to assess the accuracy of a small-footprint tilt approach and a large field-of-view hybrid approach for a total of 48 targeted needle insertions. 3D US image quality was evaluated in a healthy volunteer and compared to a commercially available matrix array US probe.

RESULTS

A mean positioning error of 1.85 ± 1.33 mm was observed when performing compound joint manipulations with the mechanical tracking system. A combined approach for navigation that incorporated the motorized movement and the in-plane tracking system corrections performed the best with a mean tip error of 3.77 ± 2.27 mm and 4.27 ± 2.47 mm based on 3D US and CBCT images, respectively. No significant differences were observed between hybrid and tilt image acquisition geometries with all mean registration errors ≤1.2 mm. 3D US volunteer images resulted in clear reconstruction of clinically relevant anatomy.

CONCLUSIONS

A mechanically tracked system with geometrically variable 3D US provides a utility that enables enhanced applicator guidance, placement verification, and improved clinical workflow during focal liver tumor ablation procedures. Evaluations of the tracking accuracy, targeting capabilities, and clinical imaging feasibility of the proposed 3D US system, provided evidence for clinical translation. This system could provide a workflow for improving applicator placement and reducing local cancer recurrence during interventional procedures treating liver cancer and has the potential to be expanded to other abdominal interventions and procedures.

Follow-up of percutaneous microwave (MW) ablation of hepatic lesion: predictive value of CT at 24-h compared with CT at 1 month

To retrospectively assess the predictive value of the CT performed at 24 h, compared with the CT performed at 1 month, in the evaluation of the technical success of microwave (MW) ablation of hepatic lesions. In a single center, 50 patients with HCC underwent percutaneous MW ablation between November 2016 and March 2019. Each patient underwent a contrast-enhanced CT exam at 24 h and at 1 month after the procedure. For each patient, was assessed the presence or absence of residual disease, the appearance of a new lesion, complications, and the involvement of the hepatic capsule, both at 24-h and at 1 month. Overall correlation between residual disease, appearance of a new nodule and complications was also assessed. A total of 50 hepatic lesions were treated with US-guided MW ablation. Patients' mean age was 70.9 years (range 28-87 years). Mean nodule diameter was 17.6 mm (range 7-35 mm). Contingency tables and the χ² test showed a strong association when looking at capsule involvement (accuracy: 100%), residual disease (accuracy: 90%; p-value 0.003), and the appearance of a new HCC nodule (accuracy: 88%; p-value 0.007); regarding complications, the accuracy was 78% (p-value 0.014). Optimal correlation was reached in 62% of cases, moderate correlation in 26%, minimum correlation in 10% of cases; no cases of zero correlation were recorded. CT at 24 h and 1 month showed comparable efficacy in evaluating residual disease after MW thermal ablation of liver lesions. However, further studies are needed to assess which factors may cause false-negative results at the 24-h CT.

Hepatic Artery Thrombosis: A Rare Complication of Microwave Ablation in Hepatocelluar Carcinoma

Microwave ablation (MWA) has become a popular therapeutic technique in hepatocellular carcinoma (HCC) alongside cryoablation, radiofrequency ablation, and liver resection/transplantation in patients with limited tumor burden. Generally well tolerated, and not as invasive as surgery, the technique results in low mortality and complication rates. We report the exceedingly rare complication of hepatic artery thrombosis with subsequent fatal ischemia of the left hepatic lobe in a 64-year-old female with cirrhosis and HCC who underwent MWA. 

A Review of Hepatocellular Carcinoma in Elderly Patients Focused on Management and Outcomes

Recent studies report a significant age-specific increase in hepatocellular carcinoma (HCC) development among persons over 75 years old. Therefore, there is an urgent need to determine the optimal treatment strategy in elderly patients with HCC. This systemic review examines the clinical characteristics, efficacy, and safety of first-line treatment modalities. The literature was searched regarding epidemiology and clinical outcomes in elderly patients (age ≥75 years) undergoing first-line treatment for HCC. Causative or comorbid conditions of HCC in elderly patients differed from those in younger patients. Radiofrequency ablation may be effective and safe in early stages. Surgical resection may also be feasible in the early stages for selected patients. Transarterial chemoembolization may be safe and effective for intermediate HCC, and sorafenib may be feasible in elderly patients with advanced HCC. Prospective randomized trials are needed to establish the treatment strategy for elderly patients with HCC.

A review of conventional and newer generation microwave ablation systems for hepatocellular carcinoma

Although microwave ablation (MWA) exhibits a high thermal efficiency, the major limitation of conventional MWA systems is the lack of predictability of the ablation zone size and shape. Therefore, a specific newer generation MWA system, The Emprint™ Ablation System with Thermosphere™ Technology, was designed to create predictable large spherical zones of ablation that are not impacted by varying tissue environments. The time required for ablation with MWA systems is short, and the shape of the necrosis is elliptical with the older systems and spherical with the new system. In addition, because MWA has no heat-sink effect, it can be used to ablate tumors adjacent to major vessels. Although these factors yield a large ablation volume and result in good local control, excessive ablation of liver tissue and unexpected ablation of surrounding organs are possible. Therefore, MWA should be carefully performed. This review highlights the efficacy and complications of MWA performed with conventional systems and the newer generation system in patients with hepatocellular carcinoma (HCC). MWA with the newer generation system seems to be a promising treatment option for large HCCs and secondary hepatic malignancies, with several advantages over other available ablation techniques, including conventional MWA. However, further randomized controlled trials are necessary to fully clarify the benefits and pitfalls of this new system.

3D visualization ablation planning system assisted microwave ablation for hepatocellular carcinoma (Diameter >3): a precise clinical application

Background

The aim of this retrospective study was to compare the feasibility and efficiency of ultrasound-guided percutaneous microwave ablation (US-PMWA) assisted by three-dimensional visualization ablation planning system (3DVAPS) and conventional 2D planning for hepatocellular carcinoma (HCC) (diameter > 3 cm).

Methods

One hundred thirty patients with 223 HCC nodules (5.0 ± 1.5 cm in diameter, [3.0–10.0 cm]) who met the eligibility criteria divided into 3D and 2D planning group were reviewed from April 2015 to August 2018. Ablation parameters and oncological outcomes were compared, including overall survival (OS), recurrence-free survival (RFS), and local tumor progression (LTP). Multivariate analysis was performed on clinicopathological variables to identify the risk factors for OS and LTP.

Results

The median follow-up period was 21 months (range 3–44). Insertion number (5.4 ± 1.2 VS. 4.5 ± 0.9, P = 0.034), ablation time (1249.2 ± 654.2 s VS. 1082.4 ± 584.7 s, P = 0.048), ablation energy (57,000 ± 11,892 J VS. 42,600 ± 10,271 J, P = 0.038) and success rate of first ablation (95.0% VS. 85.7%, P = 0.033) were higher in the 3D planning group compared with those in 2D planning group. There was no statistical difference in OS, and RFS between the two groups (P = 0.995, P = 0.845). LTP rate of 3D planning group was less than that of 2D planning group (16.5% VS 41.2%, P = 0.003). Multivariate analysis showed tumor maximal diameters (P < 0.001), tumor number (P = 0.003) and preoperative TACE (P < 0.001) were predictors for OS and sessions (P = 0.024), a-fetoprotein level (P = 0.004), and preoperative planning (P = 0.002) were predictors for LTP, respectively.

Conclusions

3DVAPS improves precision of US guided ablation resulting in lower LTP and higher 5 mm-AM for patients with HCC lesions larger than 3 cm in diameter.

Systematic review and meta-analysis of local ablative therapies for resectable colorectal liver metastases

INTRODUCTION

Local ablative therapies (LAT) have shown positive but heterogenous outcomes in the treatment of colorectal liver metastases (CRLM). The aim of this systematic review is to evaluate LAT and compare them with surgical resection.

METHODS

In accordance with PRISMA guidelines, Medline, EMBASE, Cochrane and Web of Science databases were searched for reports published before January 2019. We included papers assessing radiofrequency ablation (RFA), microwave ablation (MWA), cryoablation (CA) and electroporation (IRE) treating resectable CRLM with curative intention. We evaluated LAT related complications and oncological outcomes as tumour progression (LTP), disease-free survival (DFS) and overall survival (OS).

RESULTS

The literature search yielded 6767 records; 20 papers (860 patients) were included. No included studies related mortality with LAT. Median adverse events percentage was 7%: (8% RFA;7% MWA). Median 3y-DFS was 32% (24% RFA; 60% MWA); 5y-DFS was 27%: (18% RFA; 38.5% MWA). Median 3y-OS was 59% (60% RFA; 70% MWA; 34% CA), 5y-OS was 44.5% (43% RFA; 55% MWA; 20% CA). Surgical resection showed decreased LTP, improved DFS and OS than those reported with LAT, with RFA accounting for reduced 1y-DFS (RR 0.83, 95%CI 0.71-0.98), 3y-DFS (RR 0.5, 95%CI 0.33-0.76), 5y-DFS (RR 0.53, 95%CI 0.28-0.98) and 5y-OS (RR 0.76, 95%CI 0.58-0.98) in comparison with surgical resection.

CONCLUSIONS

Low quality evidence suggests that both RFA and MWA seem superior to CA. MWA presents similar adverse events when compared to RFA with a possible increase in DFS and OS. Surgical resection still seems to provide superior DFS and OS in comparison with LAT.

The Combination Strategy of Transarterial Chemoembolization and Radiofrequency Ablation or Microwave Ablation against Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the most common primary cancer of the liver. Hepatectomy and liver transplantation (LT) are regarded as the radical treatment, but great majority of patients are already in advanced stage on the first diagnosis and lose the surgery opportunity. Multifarious image-guided interventional therapies, termed as locoregional ablations, are recommended by various HCC guidelines for the clinical practice. Transarterial chemoembolization (TACE) is firstly recommended for intermediate-stage (Barcelona Clinic Liver Cancer (BCLC) B class) HCC but has lower necrosis rates. Radiofrequency ablation (RFA) is effective in treating HCCs smaller than 3 cm in size. Microwave ablation (MWA) can ablate larger tumor within a shorter time. Combination of TACE with RFA or MWA is effective and promising in treating larger HCC lesions but needs more clinical data to confirm its long-term outcome. The combination of TACE and RFA or MWA against hepatocellular carcinoma needs more clinical data for a better strategy. The characters and advantages of TACE, RFA, MWA, and TACE combined with RFA or MWA are reviewed to provide physician a better background on decision.

Laparoscopic hepatectomy assisted by a flexible 915 MHz microwave antenna: A safe and innovative device for hepatectomy

BACKGROUND

The objective of the present study was to elaborate a flexible 915 MHz microwave antenna (F915 MMA) and to evaluate the safety and feasibility in laparoscopic hepatecyomy (LH).

METHODS

The F915 MMA was redesigned based on the experiences in clinical practice. Ten porcine LHs were divided into a 'flexible' group and a control group, with 5 porcine LHs in each group. The F915 MMA was used in the flexible group. The data for 48 patients who underwent LH were analyzed; 12 patients underwent F915 MMA-assisted LH and were regarded as the flexible group, and the others were considered as controls.

RESULTS

The F915 MMA bends freely and rotates flexibly. In the porcine LH in vivo, the flexible group had less intraoperative blood loss (54.00 ± 27.02 ml vs 230.00 ± 83.67 ml, P = 0.002), and the mean duration of hepatic parenchyma transection in the flexible group was significantly shorter than that in the control group (17.3 ± 7.8min vs 37.9 ± 6.4min). Among th patients, compared to the control group, the flexible group had less intraoperative blood loss (154.17 ± 68.95 ml vs 284.86 ± 294.68 ml, P = 0.018), less frequency and duration of the first porta hepatic occlusion (1.50 ± 0.52times vs 2.35 ± 1.14times, P = 0.021 and 22.50 ± 7.83min vs 35.95 ± 17.23min, P = 0.017, respectively) and lower accumulative complications (33.3% vs 80.5%, P = 0.008).

CONCLUSIONS

Laparoscopic F915 MMA is an innovative device that can assist LH in a safe, feasible and flexible manner.

Role of Radiotherapy in the Treatment of Hepatocellular Carcinoma

The role of radiotherapy in the treatment of hepatocellular carcinoma (HCC) has evolved over the past few decades with the advancement of technology and improved imaging. Radiotherapy can offer high local control rates in unresectable HCC, including cases with major vascular involvement, and can provide a modality to help bridge patients to potentially curative resection or transplantation. In metastatic cases, radiotherapy can provide good palliation. This review focuses on the common radiotherapy treatment modalities used for HCC, provides outcome comparisons of these radiotherapy techniques to outcomes with other treatment modalities for HCC, and highlights the discrepancy of the role of radiotherapy in HCC amongst the current available treatment guidelines.

Propofol Compared to Midazolam Sedation and to General Anesthesia for Percutaneous Microwave Ablation in Patients with Hepatic Malignancies: A Single-Center Comparative Analysis of Three Historical Cohorts

Purpose

In percutaneous ablation procedures, periprocedural pain, unrest and respiratory concerns can be detrimental to achieve a safe and efficacious ablation and impair treatment outcome. This study aimed to compare the association between anesthetic technique and local disease control in patients undergoing percutaneous microwave ablation (MWA) of colorectal liver metastases (CRLM) and hepatocellular carcinoma (HCC).

Materials and Methods

This IRB-exempted single-center comparative, retrospective analysis of three cohorts analyzed 90 patients treated for hepatic malignancies from January 2013 until September 2018. The local tumor progression-free survival (LTPFS), safety and periprocedural pain perception were assessed using univariate and multivariate Cox proportional hazard regression analyses to correct for potential confounders.

Results

In 114 procedures (22 general anesthesia; 32 midazolam; 60 propofol), 171 liver tumors (136 CRLM; 35 HCC) were treated with percutaneous MWA. Propofol and general anesthesia were superior to midazolam/fentanyl sedation regarding LTPFS (4/94 [4.3%] vs. 19/42 [45.2%] vs. 2/35 [5.7%]; P < 0.001, respectively). Local tumor progression rate was 14.6% (25/171). Eighteen tumors (72.0%) were retreated by ablation. Of them, 14 (78%) were previously treated with midazolam. Propofol versus midazolam (P < 0.001), general anesthesia versus midazolam (P = 0.016), direct postprocedural visual analog pain score above 5 (P = 0.050) and more than one tumor per procedure (P = 0.045) were predictors for LTPFS. Multivariate analysis revealed that propofol versus midazolam (HR 7.94 [95% CI 0.04–0.39; P < 0.001]) and general anesthesia versus midazolam (HR 6.33 [95% CI 0.04–0.69; P = 0.014]) were associated with LTPFS. Pain during and directly after treatment was significantly worse in patients who received midazolam sedation (P < 0.001).

Conclusions

Compared to propofol and general anesthesia, midazolam/fentanyl sedation was associated with an increased periprocedural perception of pain and lower local tumor progression-free survival. To reduce the number of repeat procedures required to eradicate hepatic malignancies, general anesthesia and propofol sedation should be favored over midazolam.

Radiofrequency Ablation and Microwave Ablation in Liver Tumors: An Update

This article provides an overview of radiofrequency ablation (RFA) and microwave ablation (MWA) for treatment of primary liver tumors and hepatic metastasis. Only studies reporting RFA and MWA safety and efficacy on liver were retained. We found 40 clinical studies that satisfied the inclusion criteria. RFA has become an established treatment modality because of its efficacy, reproducibility, low complication rates, and availability. MWA has several advantages over RFA, which may make it more attractive to treat hepatic tumors. According to the literature, the overall survival, local recurrence, complication rates, disease-free survival, and mortality in patients with hepatocellular carcinoma (HCC) treated with RFA vary between 53.2 ± 3.0 months and 66 months, between 59.8% and 63.1%, between 2% and 10.5%, between 22.0 ± 2.6 months and 39 months, and between 0% and 1.2%, respectively. According to the literature, overall survival, local recurrence, complication rates, disease-free survival, and mortality in patients with HCC treated with MWA (compared with RFA) vary between 22 months for focal lesion >3 cm (vs. 21 months) and 50 months for focal lesion ≤3 cm (vs. 27 months), between 5% (vs. 46.6%) and 17.8% (vs. 18.2%), between 2.2% (vs. 0%) and 61.5% (vs. 45.4%), between 14 months (vs. 10.5 months) and 22 months (vs. no data reported), and between 0% (vs. 0%) and 15% (vs. 36%), respectively. According to the literature, the overall survival, local recurrence, complication rates, and mortality in liver metastases patients treated with RFA (vs. MWA) are not statistically different for both the survival times from primary tumor diagnosis and survival times from ablation, between 10% (vs. 6%) and 35.7% (vs. 39.6), between 1.1% (vs. 3.1%) and 24% (vs. 27%), and between 0% (vs. 0%) and 2% (vs. 0.3%). MWA should be considered the technique of choice in selected patients, when the tumor is ≥3 cm in diameter or is close to large vessels, independent of its size. IMPLICATIONS FOR PRACTICE: Although technical features of the radiofrequency ablation (RFA) and microwave ablation (MWA) are similar, the differences arise from the physical phenomenon used to generate heat. RFA has become an established treatment modality because of its efficacy, reproducibility, low complication rates, and availability. MWA has several advantages over RFA, which may make it more attractive than RFA to treat hepatic tumors. The benefits of MWA are an improved convection profile, higher constant intratumoral temperatures, faster ablation times, and the ability to use multiple probes to treat multiple lesions simultaneously. MWA should be considered the technique of choice when the tumor is ≥3 cm in diameter or is close to large vessels, independent of its size.

Comparison of parallel and crossed placement of antennas in microwave ablation of 3-5 cm hepatocellular carcinoma

PURPOSE

To evaluate the effects of ablation strategies on local tumor progression (LTP) after microwave ablation (MWA) of hepatocellular carcinomas (HCCs) measuring 3-5 cm.

MATERIALS AND METHODS

Between December 2011 and May 2017, 71 HCC patients with 71 nodules treated by ultrasound(US)-guided percutaneous MWA were divided into parallel (group A) and crossed (group B) antenna placement groups. All patients underwent MWA using two antennas with four insertions. LTP and overall survival (OS) rates were compared between the two groups.

RESULTS

The median follow-up time was 16.8 months. There was no significant difference in the complete ablation rate and treatment sessions between the two groups. LTP was diagnosed in 8 of 48 nodules (16.7%) in group A and 1 of 23 nodules (4.3%) in group B, with no significant difference between two groups (P = 0.115). The 1-, 2-, and 3-year OS rates were 88.5%, 79%, and 71.8% in group A and 93.8%, 87.5%, and 87.5% in group B, respectively (P = 0.236). Multivariate analysis showed that the tumor diameter (P = 0.017), the distance between the antennas (P = 0.032), and the total emission time (P = 0.015) were associated with LTP.

CONCLUSIONS

There were trends with lower LTP and improved OS in group B, despite the lack of statistically significant differences between the two strategies at a level of P < 0.05. The increase of distance between antennas and total emission time will facilitate reductions in LTP rate.

Development of a Model for Training and Assessing Open Image-Guided Liver Tumor Ablation

BACKGROUND

Image-guided microwave ablation (MWA) is a technically demanding procedure, involving advanced visual-spatial perception skills. This study sought to create and evaluate a low-cost model and training curriculum for open ultrasound-guided liver tumor MWA.

METHODS

Simulated tumors were created, implanted into bovine livers, and visualized by ultrasound. A high-fidelity abdominal model was constructed, with a total cost of $30. Experienced physicians in MWA performed simulated ablations and evaluated the model. Expert performance metrics were established and served as targets for our training curriculum. These included time, number of passes, number of repositionings, and percentage of tumor ablated. Next, 8 novice trainees completed our deliberate practice curriculum. Participants' performances were recorded throughout.

RESULTS

Physicians completed a structured feedback questionnaire rating the model's realism and training utility at 8/10 and 10/10, respectively. Tumors appeared hyperechoic and were clearly visualized on ultrasound. Trainees performed a total of 32 ablations. Our trainees' performance improved significantly in all outcomes of interest in the postcurriculum ablations compared to precurriculum ablations.

CONCLUSION

We have created a cost-effective, high-fidelity model of MWA, with a deliberate practice curriculum. Trainees can practice to proficiency with clear target metrics prior to participating in clinical cas.