Early Outcomes with Single-antenna High-powered Percutaneous Microwave Ablation for Primary and Secondary Hepatic Malignancies: Safety, Effectiveness, and Predictors of Ablative Failure

Abstract

Objective: Microwave ablation (MWA) of liver malignancies has gained much traction over the past 5 years. However, MWA carries relatively higher rates of residual disease compared to resection. Likelihood of MWA success is multifactorial and newer devices with more reliable ablation zones are being developed to overcome these drawbacks. This manuscript is a review of our first 100 liver ablations with the newer single antenna high powered MWA system. Materials and Methods: Retrospective chart review of patients that underwent MWA for either primary or secondary hepatic malignancies between March 2015 and July 2016 was conducted. The complete ablation rates, rate of new lesions, complications, and short-term survival were analyzed. Multiple statistical tests, including multivariate regression, were used to assess risk factors for local residual and recurrent disease. Results: Fifty-three patients (median age 61 ± 9 years, 39 males) underwent 100 MWAs. Of the 100 lesions ablated, 76 were hepatocellular cancers (HCCs) and 24 were metastases. Median lesion size was 16 ± 9 mm. Seventy- five of these patients had multifocal disease targeted in the same session. Seventy patients had cirrhosis (median model for end-stage liver disease score 9 ± 3; Child-Pugh B and C in 42%). An 83% complete lesion ablation rate was seen on follow-up imaging with liver protocol magnetic resonance imaging/computed tomography (median follow-up of 1 year). The minor complication rate was 9.4% with no major complications or 30-day mortality. Despite this, evidence of new foci of hepatic disease was found in 47% of patients, the majority (80%) of which were in HCC patients (P < 0.01) and most of these new lesions were in a different hepatic segment (64%). Degree of cirrhosis (P < 0.01), presence of non-alcoholic steatohepatitis (NASH) (P = 0.01) and lesion’s subcapsular location (P = 0.03) was significant predictors of residual disease. With the subset analysis of only HCC lesions larger than 1 cm, only the presence of NASH remained significant. Conclusion: The single probe high power MWA of malignant hepatic lesions is safe and effective with minimal morbidity. Degree of cirrhosis, NASH, and subcapsular location was associated with an increased rate of residual disease on short-term follow-up.

Comparing the Safety and Efficacy of Microwave Ablation Using ThermosphereTM Technology versus Radiofrequency Ablation for Hepatocellular Carcinoma: A Propensity Score-Matched Analysis

“…Several studies have compared the efficacy of first-generation MWA to that of RFA, which revealed that MWA had comparable safety and long-term efficacy for liver tumors with a diameter of <4 cm [ 18 , 19 , 26 ]. New MWA technologies have also been developed and attracted significant interest regarding their safety and efficacy, although there are few reports regarding new MWA technologies as appropriate treatment strategies [ 20 , 21 , 22 , 27 ]. To the best of our knowledge, this is the first study to evaluate the short-term and medium-term survival, efficacy and safety of MWA.…”

“…Thus, the smaller number of antenna insertions makes MWA an attractive locoregional treatment for HCC. Moreover, the ablation area of MWA can be precisely controlled based on time and output power [ 21 , 22 ], which permits a single MWA antenna to treat small nodules (<1 cm) and larger nodules up to a size of 4 cm.…”

“…Recent improvements in MWA technology have been able to provide large and spherical treatment areas. For example, a high-powered (2.4 GHz) single-antenna MWA system has been developed using Thermosphere TM technology (Emprint TM system; Covidien, Boulder, CO, USA) and has been used clinically [ 20 , 21 , 22 ]. Thermosphere TM technology provides thermal, field and wavelength control, which allows the system to produce reliable and large spherical ablation zones [ 20 ].…”

“…Thermosphere TM technology provides thermal, field and wavelength control, which allows the system to produce reliable and large spherical ablation zones [ 20 ]. Furthermore, this system provides theoretical benefits by overcoming issues with tissue charring and the heat sink effect [ 21 , 22 ]. However, we are not aware of any definitive evidence that supports the superiority of MWA using Thermosphere TM technology over RFA.…”

On Efficacy of Microwave Ablation in the Thermal Treatment of an Early-Stage Hepatocellular Carcinoma

“…The initial MWA systems were constrained by poor antenna design and the inability to achieve spherical ablation zones, causing significant damage to adjacent healthy tissues [ 45 , 46 ]. The major limitation of earlier MWA devices is the lack of predictability of the ablation zone size and shape, since it depends on the inherent characteristics of the target tissues.…”