International multicentre prospective study on microwave ablation of liver tumours: preliminary results

Efficacy of percutaneous microwave ablation guided by contrast-enhanced and two-dimensional ultrasound for in hepatic alveolar echinococcosis in difficult/dangerous locations

Background

Ultrasound-guided microwave ablation (MWA) has become a popular method for treating malignant liver tumors. However, few studies have investigated its use in the treatment of hepatoalveolar echinococcosis (HAE). This study aimed to explore the effectiveness and safety of contrast-enhanced ultrasound combined with two-dimensional ultrasound-guided MWA for the treatment of HAE in difficult/dangerous locations.

Methods

Data from 81 patients, who were diagnosed with hepatic alveolar hydatid disease in difficult/dangerous locations between January 2018 and January 2023, and underwent contrast-enhanced ultrasonography combined with two-dimensional ultrasound-guided MWA, were analyzed. After undergoing MWA, patients were followed up to determine whether the lesions recurred and to evaluate the therapeutic effect of MWA. Preoperatively, individualized strategies were designed for lesions in different locations, and different auxiliary ablation technologies were used for contrast-enhanced ultrasound combined with two-dimensional ultrasound-guided MWA to achieve complete inactivation of lesions in difficult/dangerous locations.

Results

MWA was performed on 89 HAE lesions in 81 patients. The median diameter of the lesions was 2.86 cm (interquartile range [IQR] 2.36-3.49 cm). The complete ablation rate after surgery was 100%, with a recurrence rate of 11.11%, and median follow-up of 24 months (IQR 12-48 months). The incidence of minor complications was 14.81%; no serious complications or deaths occurred. Compared with before surgery, TB, DB, alanine aminotransferase, and aspartate aminotransferase levels increased (p < 0.001), albumin platelets and activated partial thromboplastin time decreased (p < 0.05), with no statistical difference in prothrombin time (p > 0.05).

Conclusion

MWA may be a safe and effective method for treating HAE in difficult/dangerous locations, and may represent a new and alternative option for this patient population.

Intraoperative liver deformation and organ motion caused by ventilation, laparotomy, and pneumoperitoneum in a porcine model for image-guided liver surgery

BACKGROUND

Image-guidance promises to make complex situations in liver interventions safer. Clinical success is limited by intraoperative organ motion due to ventilation and surgical manipulation. The aim was to assess influence of different ventilatory and operative states on liver motion in an experimental model.

METHODS

Liver motion due to ventilation (expiration, middle, and full inspiration) and operative state (native, laparotomy, and pneumoperitoneum) was assessed in a live porcine model (n = 10). Computed tomography (CT)-scans were taken for each pig for each possible combination of factors. Liver motion was measured by the vectors between predefined landmarks along the hepatic vein tree between CT scans after image segmentation.

RESULTS

Liver position changed significantly with ventilation. Peripheral regions of the liver showed significantly higher motion (maximal Euclidean motion 17.9 ± 2.7 mm) than central regions (maximal Euclidean motion 12.6 ± 2.1 mm, p < 0.001) across all operative states. The total average motion measured 11.6 ± 0.7 mm (p < 0.001). Between the operative states, the position of the liver changed the most from native state to pneumoperitoneum (14.6 ± 0.9 mm, p < 0.001). From native state to laparotomy comparatively, the displacement averaged 9.8 ± 1.2 mm (p < 0.001). With pneumoperitoneum, the breath-dependent liver motion was significantly reduced when compared to other modalities. Liver motion due to ventilation was 7.7 ± 0.6 mm during pneumoperitoneum, 13.9 ± 1.1 mm with laparotomy, and 13.5 ± 1.4 mm in the native state (p < 0.001 in all cases).

CONCLUSIONS

Ventilation and application of pneumoperitoneum caused significant changes in liver position. Liver motion was reduced but clearly measurable during pneumoperitoneum. Intraoperative guidance/navigation systems should therefore account for ventilation and intraoperative changes of liver position and peripheral deformation.

Colorectal Liver Metastases: A Literature Review of Viable Surgical Options with a Special Focus on Microwave Liver Thermal Ablation and Mini-Invasive Approach

Colorectal cancer (CRC) is the third most common tumor worldwide and it is characterized in 20-30% of cases by liver involvement, which strongly affects the long-term patient outcome. There are many available therapies for liver colorectal metastases (CRLMs); the current standard of care is represented by liver resection, and when feasible, associated with systemic chemotherapy. Microwave thermal ablation (MWA) is a viable option in unresectable patients or to achieve treatment with a parenchymal spearing approach. A literature review was performed for studies published between January 2000 and July 2022 through a database search using PUBMED/Medline and the Cochrane Collaboration Library with the following MeSH search terms and keywords: microwave, ablation, liver metastases, colorectal neoplasm, and colon liver rectal metastases. The recurrence rate and overall patients' survival were evaluated, showing that laparoscopic MWA is safe and effective to treat CRLMs when resection is not feasible, or a major hepatectomy in fragile patients is necessary. Considering the low morbidity of this procedure, it is a viable option to treat patients with recurrent diseases in the era of effective chemotherapy and multimodal treatments.

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.

Operative Microwave Ablation for Hepatocellular Carcinoma Within 3 cm and 3 Nodules: Experience in 559 Patients

BACKGROUND

There are few published data regarding long-term outcome survival after microwave ablation (MWA) for hepatocellular carcinoma (HCC) within 3 cm and 3 nodules. The aim of this study was to examine long-term outcomes after operative MWA for HCC within 3 cm and 3 nodules.

METHODS

This cohort of this retrospective study comprised 559 patients who underwent operative MWA for HCC within 3 cm and 3 nodules in our institute between 1996 and 2017. We analyzed overall survival (OS) and recurrence-free survival (RFS), and evaluated factors related to prognosis.

RESULTS

Median follow-up time was 69 months for the entire cohort. OS rates were 1-year: 98%, 3-year: 87%, 5-year: 73%, and 10-year:39%; RFS rates were 1-year: 91%, 3-year: 60%, 5-year: 42%, and 10-year: 21%. Multivariate analysis revealed that hepatitis C virus (HCV)-positive status, ALBI grade 2 or 3, maximum tumor diameter ≥ 20 mm, and multiple nodules were independent risk factors for both OS and RFS. A prognostic staging model using one point for each risk factor provided a well-categorized predictive model. The 5-year OS rates were 93%, 81%, and 57% for scores of 0, 1 or 2, and 3 or 4, respectively (P < 0.001). The 5-year RFS rates were 70%, 48%, and 28% for scores of 0, 1 or 2, and 3 or 4, respectively (P < 0.001).

CONCLUSIONS

Our results revealed good long-term outcomes after operative MWA for HCC within 3 cm and 3 nodules.

Percutaneous microwave ablation versus radiofrequency ablation of hepatocellular carcinoma: a meta-analysis of randomized controlled trials

PURPOSE

Percutaneous radiofrequency ablation (RFA) and microwave ablation (MWA) are well-validated interventions for hepatocellular carcinoma (HCC). The purpose of this study was to compare their safety and efficacy through a meta-analysis of randomized controlled trials (RCT).

METHODS

MEDLINE, Pubmed, and the Cochrane Library were queried up to September 2020 using the terms "microwave", "radiofrequency", "hepatocellular", and "randomized". Only RCTs investigating MWA versus RFA for HCC were included. Baseline study characteristics, complete ablation rate, ablation time, overall survival, local recurrence, and complication rates were investigated.

RESULTS

Among the five original studies included, a total of 413 and 431 patients were treated with RFA and MWA, respectively. All studies focused on very early and early-stage HCC only (Barcelona Clinic Liver Cancer Stage 0 and A). No statistical significance was observed in terms of complete ablation rate (96.7 vs 96.9%, p = 0.882), overall survival (6 month: 95.7 vs 100%, p = 0.492; 1 year: 91.9 vs 94.1%, p = 0.264; 3 year: 77.5 vs 78.4%, p = 0.905), recurrence-free survival (6 month: 99.1 vs 99.7%, p = 0.717; 1 year: 94.6 vs 93.9%, p = 0.675; 3 year: 76.8 vs 77.1%, p = 0.935), and complication rates (p > 0.05 in all types). The mean ablation time of MWA was significantly shorter than RFA (26.9 vs 14.1 min, p < 0.001).

CONCLUSION

For very early and early-stage HCC, RFA and MWA are equally safe and effective, though the former is associated with a longer ablation time.

Combined trans-arterial embolisation and microwave ablation for the treatment of large unresectable hepatic metastases (>3 cm in maximal diameter)

PURPOSE

To assess the safety and efficacy of a two-step single-session procedure, combining transarterial embolization (TAE) and percutaneous microwave ablation (MWA), in the treatment of > 3 cm unresectable liver metastases. We also compared the final volume obtained by the two techniques (V_E-T) and the expected ablation volume of the stand-alone MWA (V_T).

METHODS

From January 2015 to December 2017, 22 consecutive patients, with a total of 24 unresectable hepatic metastases >3 cm in diameter underwent a two-step single-session combined treatment of TAE and MWA. Follow-up computed tomography scans were performed at 1-, 3-, 6-, 12, and 24 months post-procedure. V_E-T as final ablation volume induced by the combined treatment (TAE-MWA), V_N as initial nodule volume, V_T as expected ablation volume of MWA treatment alone were evaluated and compared.

RESULTS

Tumor dimensions ranged from 32 to 73 mm. Technical success was achieved in all treated tumors with no local tumor recurrence. Final ablation volumes ranged from 50 to 450 cm³ and the short-axis diameter of the ablation zone ranged from 12 to 48 mm. The mean ΔV increment in the final ablation volume with respect to the stand-alone MWA was 196% (ranging from 25 cm³ - 210 cm³) (p < 0.05). The V_E-T mean was four times the V_N mean, while the V_T mean was about twice the V_N mean. No recurrence and only one case of post-embolization bleeding were observed.

CONCLUSIONS

This study demonstrated the safety and efficacy of a combined two-step single-session TAE-MWA treatment of unresectable hepatic metastases > 3 cm in diameter.

Feasibility and safety of surgical microwave ablation for hepatocellular carcinoma in elderly patients: a single center analysis in Japan

The feasibility and safety of microwave ablation in elderly hepatocellular carcinoma (HCC) patients remains unknown. The aim of this study was to evaluate the feasibility and safety of surgical microwave ablation for HCC in patients older than 80 years of age. This retrospective study enrolled consecutive 114 patients older than 80 years of age who underwent surgical microwave ablation for HCC between July 1994 and December 2017. We analyzed perioperative outcomes and long-term outcomes to clarify the prognostic factors. The 1-, 3-, 5-year overall survival and recurrence-free survival rates were 97.3%, 76.0%, 49.2% and 84.2%, 44.7%, and 32.5%, respectively. The overall major morbidity rates (Clavien–Dindo grade IIIA or above) were 2.6%. There were no cases of mortality. Multivariate analysis showed that hepatitis C virus antibody (HCV-Ab) positivity and the presence of multiple tumors were independent prognostic factors for long-term outcomes. The overall survival rate of patients with HCV-Ab negative and single tumor was better than that of other patients (p = 0.026). Surgical microwave ablation was feasible and safe for elderly patients with HCC. Elderly patients with HCV-Ab negative and single tumor would be expected to have better long-term outcomes after surgical microwave ablation.

Efficacy of surgical microwave ablation for recurrent hepatocellular carcinoma after curative hepatectomy

BACKGROUND

Little evidence exists regarding postrecurrence survival after microwave ablation for recurrent hepatocellular carcinoma (HCC) after curative hepatectomy; we aimed to evaluate the feasibility of surgical microwave ablation.

METHODS

In this retrospective review, we enrolled patients who underwent curative hepatectomy for primary HCC in our department and had intrahepatic recurrence. We analyzed overall survival according to treatment modality to clarify the prognostic factors for survival.

RESULTS

Of 257 patients, 119 had intrahepatic recurrence. Three patients underwent repeat hepatectomy; 75 patients underwent surgical microwave ablation, and 34 patients underwent transcatheter arterial chemoembolization or hepatic arterial infusion chemotherapy. The median postrecurrence survival time and 5-year postrecurrence survival after surgical microwave ablation were 37.4 months and 55.4%, respectively. The major complication rate (Clavien-Dindo classification IIIa or above) after surgical microwave ablation was 5.3% with no mortality. Multivariate analysis showed that microvascular invasion at primary tumors, and recurrent tumors within 3 cm and 3 nodules were independent prognostic factors for overall survival after surgical microwave ablation for recurrent HCC.

CONCLUSION

Our results suggested that surgical microwave ablation is safe and feasible for recurrent intrahepatic HCC after curative hepatectomy. Close follow-up and further curative treatment could be important for improving postrecurrence survival.

Videolaparoscopic microwave ablation in patients with HCC at a European high-volume center: Results of 815 procedures

BACKGROUND

Videolaparoscopic (VL) microwave ablation (MWA) is not included in most of the international guidelines as a therapeutic option for hepatocellular carcinoma (HCC). Aim of this study was to assess the safety of VL MWA in patients with HCC for whom resection or percutaneous ablation is unsuitable.

METHODS

A retrospective analysis was performed on a prospective database of patients with HCC treated with VL MWA at our institution from 2009 to 2016. Patient demographics, operational characteristics, and complications were recorded. Statistical analysis was performed to identify safety profile, overall survival and recurrence rate.

RESULTS

A total of 815 VL MWA were performed in 674 patients with a mean age of 64 years. Patients had a mean Model for End-stage Liver Disease score of 10 (±3); 32.8% were Child B, 44.1% Barcelona Clinic Liver Cancer B-C. Perioperative mortality was 0.4%. Overall morbidity was 30.8%, with Dindo-Clavien complications ≥3 in 2%. The median length of stay was 2 days. In 43.1% VL MWA was the first-line therapy. Overall 1-, 3-, and 5-year survival rates were 81.9%, 54.9%, and 35.9%.

CONCLUSIONS

The present is the largest series of VL ablation and the bigger number of patients with HCC treated with MW reported nowadays. It confirms the safety of a minimally invasive procedure for patients with HCC when resection or percutaneous ablation is not feasible.

Actual 10-Year Survival After Surgical Microwave Ablation for Hepatocellular Carcinoma: A Single-Center Experience in Japan

BACKGROUND

Little evidence exists regarding long-term survival after microwave ablation for hepatocellular carcinoma (HCC). The aim of this study is to determine actual 10-year survival and clarify the clinicopathological features of patients surviving ≥ 10 years after surgical microwave ablation.

PATIENTS AND METHODS

This retrospective study identified 459 patients who underwent surgical microwave ablation for HCC with curative intent between 2001 and 2008. We compared 100 patients who survived ≥ 10 years with 321 patients who died within 10 years.

RESULTS

Median overall survival and recurrence-free survival rates were 5.5 and 2.4 years, respectively. The actual 10-year overall survival rate was 23.8%, and the actual 10-year recurrence-free survival rate was 8.1%. Multivariate analysis showed that age > 70 years [odds ratio 1.87, P = 0.029], hepatitis C virus positivity (OR 2.30, P = 0.004), Child-Pugh class B (OR 3.28, P = 0.003), and platelet count < 10 × 10⁴ /µL (OR 1.93, P = 0.033) were independent risk factors for actual 10-year survival. During 10-year follow-up, 66% of the ≥ 10-year survivors developed recurrence, and 91% of these patients underwent further curative treatment, including hepatic resection or local ablation, for HCC recurrence.

CONCLUSION

Ten-year survival after surgical microwave ablation for HCC can be expected in approximately 24% of patients, even though nearly 2/3 of our 10-year survival patients experienced recurrence. Close postoperative follow-up and further curative treatment for recurrence are important for improving long-term survival.

Transcatheter arterial chemoembolization combined with radiofrequency or microwave ablation for hepatocellular carcinoma: a review

Hepatocellular carcinoma (HCC) is the sixth most common type of malignancy. Several therapies are available for HCC and are determined by stage of presentation, patient clinical status and liver function. Local–regional treatment options, including transcatheter arterial chemoembolization, radiofrequency ablation or microwave ablation, are safe and effective for HCC but are accompanied by limitations. The synergistic effects of combined transcatheter arterial chemoembolization and radiofrequency ablation/microwave ablation may overcome these limitations and improve the therapeutic outcome. The purpose of this article is to review the current literature on these combined therapies and examine their efficacy, safety and influence on the overall and recurrence-free survival in patients with HCC.

Microwave ablation provides better survival than liver resection for hepatocellular carcinoma in patients with borderline liver function: application of ALBI score to patient selection

BACKGROUND

Studies comparing microwave ablation (MWA) and liver resection are lacking. This study evaluates the survival of patients with hepatocellular carcinoma (HCC) treated with liver resection or MWA and the role of Albumin-Bilirubin (ALBI) score in patient selection for treatments.

METHODS

This is a retrospective analysis of patients who received curative liver resection or MWA for HCC. Propensity score matching was used at a 1:1 ratio. The value of ALBI grade for patient selection was evaluated. Overall and disease-free survival were compared between two groups.

RESULTS

Of the 442 patients underwent MWA or liver resection for HCC during the study period, 63 patients received MWA and 379 patients received liver resection. Propensity scoring matching analysis resulted in 63 matched pairs for further analysis. Subgroup analysis according to the ALBI grade was performed. Liver resection offered better overall and disease-free survivals in patients with ALBI grade 1. MWA provided a significantly better overall survival (p = 0.025) and a trend towards better disease-free survival (p = 0.39) in patients with ALBI grade 2 or 3.

CONCLUSIONS

Liver resection offered superior disease-free survival to MWA in patients with HCC. The ALBI grade could identify patients with worse liver function who might gain survival advantage from MWA.

Status and advancement of microwave ablation in China

Tumour ablation is defined as the direct application of chemical or thermal therapy to eradicate or substantially destroy a tumour. Currently, minimally invasive ablation techniques are available for the local destruction of focal tumours in multiple organ sites. Microwave ablation (MWA) is premised on the biological response of solid tumours to tissue hyperthermia, and it is a relatively low-risk procedure. Due to several advantages of MWA, including higher thermal efficiency, higher capability for coagulating blood vessels, faster ablation time and the simultaneous application of multiple antennae, MWA could be a promising minimally invasive ablation technique for the treatment of solid tumours. Therefore, the use of MWA has developed rapidly in China during the last decade. Many successful studies have been performed, and widespread use has been achieved for multiple types of tumours in China, especially for liver cancer. This review will describe the state-of-the-art of MWA in China, including the development of MWA equipment and its application in the treatment of multiple types of tumours.

Safety and advantages of combined resection and microwave ablation in patients with bilobar hepatic malignancies

BACKGROUND

The multimodality approach has significantly improved outcomes for hepatic malignancies. Microwave ablation is often used in isolation or succession, and seldom in combination with resection. Potential benefits and pitfalls from combined resection and ablation therapy in patients with complex and extensive bilobar hepatic disease have not been well defined.

METHODS

A review of the University of Louisville prospective Hepato-Pancreatico-Biliary Patients database was performed with multi-focal bilobar disease that underwent microwave ablation with resection or microwave only included.

RESULTS

One hundred and eight were treated with microwave only (MWA, n = 108) or combined resection and ablation (CRA, n = 84) and were compared with similar disease-burden patients undergoing resection only (n = 84). The groups were comparable except that the MWA group was older (p = .02) and with higher co-morbidities (diabetes, hepatitis). The resection group had larger tumours (4 vs. 3.2 and 3 cm) but the CRA group had more numerous lesions (4 vs. 3 and 2, p = .002). Short-term outcomes including morbidity (47.6% vs. 43%, p = .0715) were similar between the CRA and resection only groups. Longer operative time (164 vs. 126 min, p = .003) and need for blood transfusion (p = .001) were independent predictors of complications. Survival analyses for colorectal metastasis patients (n = 158) demonstrated better overall survival (OS) (43.9 vs. 37.6 and 30.5 months, p = .035), disease-free survival (DFS) (38 vs. 26.6 and 16.9 months, p = .028) and local recurrence-free survival (LRFS) (55.4 vs. 17 and 22.9 months, p < .001) with resection only.

CONCLUSION

The use of microwave ablation in addition to surgical resection did not significantly increase the morbidities or short-term outcomes. In combination with systemic and other local forms of therapy, combined resection and ablation is a safe and effective procedure.

Induction of rapid, reproducible hepatic ablations using next-generation, high frequency irreversible electroporation (H-FIRE) in vivo

INTRODUCTION

Irreversible electroporation (IRE) offers an alternative to thermal tissue ablation in situ. High-frequency IRE (H-FIRE), employing ultra-short bipolar electrical pulses, may overcome limitations associated with existing IRE technology to create rapid, reproducible liver ablations in vivo.

METHODS

IRE electrodes (1.5 cm spacing) were inserted into the hepatic parenchyma of swine (n = 3) under surgical anesthesia. In the absence of paralytics or cardiac synchronization five independent H-FIRE ablations were performed per liver using 100, 200, or 300 pulses (2250 V, 2-5-2 μs configuration). Animals were maintained under isoflurane anesthesia for 6 h prior to analysis of ablation size, reproducibility, and apoptotic cell death.

RESULTS

Mean ablation time was 230 ± 31 s and no EKG abnormalities occurred during H-FIRE. In 1/15 HFIRE's minor muscle twitch (rectus abdominis) was recorded. Necropsy revealed reproducible ablation areas (34 ± 4 mm(2), 88 ± 11 mm(2) and 110 ± 11 mm(2); 100-, 200- and 300-pulses respectively). Tissue damage was predominantly apoptotic at pulse delivery ≤200 pulses, after which increasing evidence of tissue necrosis was observed.

CONCLUSION

H-FIRE can be used to induce rapid, predictable ablations in hepatic tissue without the need for intraoperative paralytics or cardiac synchronization. These advantages may overcome limitations that restrict currently available IRE technology for hepatic ablations.

Microwave ablation in primary and secondary liver tumours: technical and clinical approaches

Thermal ablation is increasingly being utilised in the treatment of primary and metastatic liver tumours, both as curative therapy and as a bridge to transplantation. Recent advances in high-powered microwave ablation systems have allowed physicians to realise the theoretical heating advantages of microwave energy compared to other ablation modalities. As a result there is a growing body of literature detailing the effects of microwave energy on tissue heating, as well as its effect on clinical outcomes. This article will discuss the relevant physics, review current clinical outcomes and then describe the current techniques used to optimise patient care when using microwave ablation systems.

Single-stage resection and microwave ablation for bilobar colorectal liver metastases

BACKGROUND

Patients undergoing liver resection combined with microwave ablation (MWA) for bilobar colorectal metastasis may have similar overall survival to patients who undergo two-stage hepatectomy, but with less morbidity.

METHODS

This was a multi-institutional evaluation of patients who underwent MWA between 2003 and 2012. Morbidity (90-day) and mortality were compared between patients who had MWA alone and those who underwent combined resection and MWA (CRA). Mortality and overall survival after CRA were compared with published data on two-stage resections.

RESULTS

Some 201 patients with bilobar colorectal liver metastasis treated with MWA from four high-volume institutions were evaluated (100 MWA alone, 101 CRA). Patients who had MWA alone were older, but the groups were otherwise well matched demographically. The tumour burden was higher in the CRA group (mean number of lesions 3·9 versus 2·2; P = 0·003). Overall (31·7 versus 15·0 per cent; P = 0·006) and high-grade (13·9 versus 5·0 per cent; P = 0·030) complication rates were higher in the CRA group. Median overall survival was slightly shorter in the CRA group (38·4 versus 42·2 months; P = 0·132) but disease-free survival was similar (10·1 versus 9·3 months; P = 0·525). The morbidity and mortality of CRA compared favourably with rates in the existing literature on two-stage resection, and survival data were similar.

CONCLUSION

Single-stage hepatectomy and MWA resulted in survival similar to that following two-stage hepatectomy, with less overall morbidity.

Microwave ablation energy delivery: influence of power pulsing on ablation results in an ex vivo and in vivo liver model

PURPOSE

The purpose of this study was to compare the impact of continuous and pulsed energy deliveries on microwave ablation growth and shape in unperfused and perfused liver models.

METHODS

A total of 15 kJ at 2.45 GHz was applied to ex vivo bovine liver using one of five delivery methods (n = 50 total, 10 per group): 25 W continuous for 10 min (25 W average), 50 W continuous for 5 min (50 W average), 100 W continuous for 2.5 min (100 W average), 100 W pulsed for 10 min (25 W average), and 100 W pulsed for 5 min (50 W average). A total of 30 kJ was applied to in vivo porcine livers (n = 35, 7 per group) using delivery methods similar to the ex vivo study, but with twice the total ablation time to offset heat loss to blood perfusion. Temperatures were monitored 5-20 mm from the ablation antenna, with values over 60 °C indicating acute cellular necrosis. Comparisons of ablation size and shape were made between experimental groups based on total energy delivery, average power applied, and peak power using ANOVA with post-hoc pairwise tests.

RESULTS

No significant differences were noted in ablation sizes or circularities between pulsed and continuous groups in ex vivo tissue. Temperature data demonstrated more rapid heating in pulsed ablations, suggesting that pulsing may overcome blood perfusion and coagulate tissues more rapidly in vivo. Differences in ablation size and shape were noted in vivo despite equivalent energy delivery among all groups. Overall, the largest ablation volume in vivo was produced with 100 W continuous for 5 min (265.7 ± 208.1 cm(3)). At 25 W average, pulsed-power ablation volumes were larger than continuous-power ablations (67.4 ± 34.5 cm(3) versus 23.6 ± 26.5 cm(3), P = 0.43). Similarly, pulsed ablations produced significantly greater length (P ≤ 0.01), with increase in diameter (P = 0.09) and a slight decrease in circularity (P = 0.97). When comparing 50 W average power groups, moderate differences in size were noted (P ≥ 0.06) and pulsed ablations were again slightly more circular.

CONCLUSIONS

Pulsed energy delivery created larger ablation zones at low average power compared to continuous energy delivery in the presence of blood perfusion. Shorter duty cycles appear to provide greater benefit when pulsing.

Microwave ablation: state-of-the-art review

This paper reviews state-of-the-art microwave ablation (MWA) of tumors. MWA is a novel method for treating inoperable tumors, ie, tumors that cannot be treated surgically. However, patients generally choose removal of the tumor by conventional techniques. A literature review of MWA for breast, liver, lung, and kidney tumors is reported here, with tabulation of our findings according to the type of technique used, with a detailed description of the time, type of microwave generator used, and number of patients treated with MWA. In some cases, the subjects were not human patients, but pig or bovine liver specimens. MWA is a technique that has proved to be promising and likely to be used increasingly in the ablation of cancerous tumors. However, MWA needs to be used more widely to establish itself as a common tool in the treatment of inoperable tumors.

Percutaneous microwave ablation vs radiofrequency ablation in the treatment of hepatocellular carcinoma

Hepatocellular cancer ranks fifth among cancers and is related to chronic viral hepatitis, alcohol abuse, steatohepatitis and liver autoimmunity. Surgical resection and orthotopic liver transplantation have curative potential, but fewer than 20% of patients are suitable candidates. Interventional treatments are offered to the vast majority of patients. Radiofrequency (RFA) and microwave ablation (MWA) are among the therapeutic modalities, with similar indications which include the presence of up to three lesions, smaller than 3 cm in size, and the absence of extrahepatic disease. The therapeutic effect of both methods relies on thermal injury, but MWA uses an electromagnetic field as opposed to electrical current used in RFA. Unlike MWA, the effect of RFA is partially limited by the heat-sink effect and increased impedance of the ablated tissue. Compared with RFA, MWA attains a more predictable ablation zone, permits simultaneous treatment of multiple lesions, and achieves larger coagulation volumes in a shorter procedural time. Major complications of both methods are comparable and infrequent (approximately 2%-3%), and they include haemorrhage, infection/abscess, visceral organ injury, liver failure, and pneumothorax. RFA may incur the additional complication of skin burns. Nevertheless, there is no compelling evidence for differences in clinical outcomes, including local recurrence rates and survival.

Long-term outcomes following microwave ablation for liver malignancies

BACKGROUND

Microwave ablation has emerged as a promising treatment for liver malignancies, but there are scant long-term follow-up data. This study evaluated long-term outcomes, with a comparison of 915-MHz and 2.4-GHz ablation systems.

METHODS

This was a retrospective review of patients with malignant liver tumours undergoing operative microwave ablation with or without liver resection between 2008 and 2013. Regional or systemic (neo)adjuvant therapy was given selectively. Local recurrence was analysed using competing-risk methods with clustering, and overall survival was determined from Kaplan-Meier curves.

RESULTS

A total of 176 patients with 416 tumours were analysed. Colorectal liver metastases (CRLM) comprised 81.0 per cent of tumours, hepatocellular carcinoma 8.4 per cent, primary biliary cancer 1.7 per cent and non-CRLM 8.9 per cent. Median follow-up was 20.5 months. Local recurrence developed after treatment of 33 tumours (7.9 per cent) in 31 patients (17.6 per cent). Recurrence rates increased with tumour size, and were 1.0, 9.3 and 33 per cent for lesions smaller than 1 cm, 1-3 cm and larger than 3 cm respectively. On univariable analysis, the local recurrence rate was higher after ablation of larger tumours (hazard ratio (HR) 2.05 per cm; P < 0.001), in those with a perivascular (HR 3.71; P = 0.001) or subcapsular (HR 2.71; P = 0.008) location, or biliary or non-CRLM histology (HR 2.47; P = 0.036), and with use of the 2.4-GHz ablation system (HR 3.79; P = 0.001). Tumour size (P < 0.001) and perivascular position (P = 0.045) remained significant independent predictors on multivariable analysis. Regional chemotherapy was associated with decreased local recurrence (HR 0.49; P = 0.049). Overall survival at 4 years was 58.3 per cent for CRLM and 79.4 per cent for other pathology (P = 0.360).

CONCLUSION

Microwave ablation of liver malignancies, either combined or not combined with liver resection, and selective regional and systemic therapy resulted in good long-term survival. Local recurrence rates were low after treatment of tumours smaller than 3 cm in diameter, and those remote from vessels.

Microwave ablation of giant hepatic cavernous hemangiomas

PURPOSE

This study was designed to explore the safety and efficacy of percutaneous microwave (MW) ablation as an alternative treatment for symptomatic giant hepatic hemangiomas.

METHODS

Patients (n = 7; 6 females, 1 male; mean age = 44 years) with symptomatic, giant hemangiomas (n = 8) were treated with ultrasound-guided percutaneous MW ablation and followed for a mean of 18 months. Patient pain was recorded both before and after the procedure according to the 10-point visual analog scale. All patients were treated using one or three gas-cooled 17-gauge antennas powered by a 2.4-GHz generator (Neuwave Medical, Madison, WI). Mean ablation time was 11.6 min. Four patients received hydrodissection to protect the abdominal wall, colon, or gallbladder (5 % dextrose in water, mean volume 900 mL). Immediate postablation biphasic CT of the abdomen was performed, and four of seven patients have undergone delayed follow-up imaging.

RESULTS

All ablations were technically successful with no major or minor complications. Average pain score decreased from 4.6 to 0.9 (p < 0.05), and six of seven patients report resolution or improvement of symptoms at 18-month average follow-up (range 1-33 months). Immediately postablation, mean tumor diameter decreased 25 % (from 7.3 to 5.5 cm, p < 0.05) and volume decreased 62 % (from 301 to 113 cm(3), p < 0.05).

DISCUSSION

In this series, percutaneous MW ablation was safe, well-tolerated, and effective in markedly shrinking large hepatic hemangiomas and improving symptoms in most patients.

Laparoscopic-assisted ablation of hepatic tumors: a review

Thermal ablation of hepatic tumors has been an evolving field over the last two decades. It is used in the treatment of both primary and metastatic neoplasms, and with evolutions in the technology, there has been an increasing interest in treating lesions where hepatic resection is not an option. Laparoscopic or minimally invasive surgical procedures have also advanced during this same time period, and the interface of these tools has been associated with the genesis of a new approach for treating hepatic lesions which are located in difficult to reach locations or found immediately adjacent to other intra-abdominal organs. This review summarizes the published literature focusing on the treatment of primary and metastatic neoplasms located in the liver, including a review of outcomes.

Microwave ablation for hepatic malignancies: a call for standard reporting and outcomes

BACKGROUND

Clinical standards of reporting microwave ablation outcomes have not been defined with regard to ablation success, 90-day morbidity, local recurrence after ablation, and nonablation hepatic recurrence. We propose recommendations for microwave ablation reporting and quality standards.

METHODS

Literature review of clinical studies focusing on microwave ablation of primary and metastatic hepatic tumors was reported.

RESULTS

Ablation success remains the highest quality reporting standard with variations in nomenclature, but with a universal agreement of complete destruction of the target lesion within 1 month after initial microwave ablation. Local recurrence after ablation remains highly variable, with reports as low as 2.2% to as high as 22%; standards lack a common, clearly defined distance from the initial target ablated lesion and the requirement that the target lesion be defined as an ablation success before it can be called a recurrence. Nonablation hepatic recurrence, nonhepatic recurrence, and 90-day morbidity and mortality remain limited in the current literature.

CONCLUSIONS

Standardization of hepatic microwave ablation reporting standards are proposed. Current reporting standards in microwave ablation of hepatic malignancies are suboptimal and lack standardization for comparison across institutions.

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

Primary liver cancer and liver metastases are among the most frequent malignancies worldwide, with an increasing number of new cases and deaths every year. Traditional surgery is only suitable for a limited proportion of patients and imaging-guided percutaneous thermal ablation has achieved optimistic results for management of hepatic malignancy. This synopsis outlines the first clinical practice guidelines for ultrasound-guided percutaneous microwave ablation therapy for hepatic malignancy, which was created by a joint task force of the Society of Chinese Interventional Ultrasound. The guidelines aim at standardizing the microwave ablation procedure and therapeutic efficacy assessment, as well as proposing the criteria for the treatment candidates.

Management of hepatocellular carcinoma with transarterial chemoembolization in the era of systemic targeted therapy

The clinical management of hepatocellular carcinoma (HCC) is often complicated by poor liver function. Treatment options for intermediate- and advanced-stage disease are limited. Transcatheter arterial chemoembolization (TACE) is an effective first-line therapy for intermediate-stage HCC. By interrupting blood flow to the tumor and administering concentrated chemotherapy locoregionally, TACE induces necrosis at the tumor site, but may create conditions that permit or encourage angiogenesis and recurrence of the tumor. Combination of TACE with new targeted agents may be an effective way to treat intermediate-stage HCC, particularly in higher risk patients. Because of the efficacy and safety of sorafenib-the first systemic therapy to show significant clinical benefit in advanced HCC-there is great interest in its potential use in combination with existing treatment modalities. The synergistic combination of TACE plus sorafenib represents a promising opportunity for tumor control.