04:12 PM Abstract No. 187 Efficacy and outcomes following percutaneous microwave ablation of hepatocellular carcinomas (HCC) measuring between 3 and 5 cm

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Tumors greater than 3 cm have been considered less favorable for local percutaneous treatment, due to association with vascular invasion and higher histologic grade. The purpose of this study was to evaluate technical success and clinical outcomes of patients with HCC between 3-5 cm treated with CT-guided percutaneous microwave ablation (MWA). An institutional database was used to identify adult patients with HCC between 3-5 cm that were treated with CT-guided percutaneous MWA between August 2008 and December 2017. Patient demographics, tumor characteristics, and patient performance status were recorded. The diagnosis of HCC was established by biopsy or imaging criteria (OPTN). Primary efficacy rate was defined as the percentage of treated tumors that showed complete ablation of macroscopic tumor on the first follow-up scan. Secondary efficacy rate was defined as the percentage of residual tumors identified on post-procedure imaging (< 60 days) that were successfully re-treated. Once primary or secondary efficacy was achieved, patients were re-imaged at approximately 3-month intervals until they were censored due to loss of follow-up, death or transplantation. 367 patients underwent 544 MWA procedures over the study period. 61 patients (50 male, 11 female), had a diagnosis of HCC and lesion size of between 3 and 5 cm. Hydrodissection was performed in 27 cases. Mean follow-up was 822 days (range 27-3191). Of 61 lesions treated, no recurrence developed in the treated lesion in 41 cases. In the remaining 20 cases, recurrence developed, with mean time to recurrence of 335 days (range 24 – 1000 days). Recurrent tumor was managed with repeat ablation and/or intra-arterial therapy. Early recurrence (< 60 days) occurred in 3 cases, and was successfully treated with repeat ablation in two patients. 15 patients went on to subsequent liver transplantation, with analysis of the explants revealing no viable residual tumor in that area in 8 cases. There were 7 minor and no major complications. Advances in thermal ablation technology now allow for treatment of larger HCCs, with this study showing primary and secondary efficacy rates of 95.1% and 98.3%, respectively.