Microwave ablation for hepatic malignancies: A multi-institutional analysis.

Abstract

218 Background: Although many hepatobiliary centers have moved from radiofrequency ablation to microwave ablation (MWA), the factors that influence local control with MWA are not well described. We hypothesized that tumor size, number of tumors, and tumor histology significantly affected MWA success and recurrence-free survival (RFS). Methods: Consecutive patients with hepatic malignancy treated by MWA were included from 4 high-volume institutions (2003-2011), and grouped by histology: hepatocellular cancer (HCC), colorectal metastases (CM), neuroendocrine metastases (NM), and other cancers. Independent significance of variables was established with logistic regression and Cox proportional hazards models. Results: Four-hundred seventy three ablation procedures were performed (139 HCC, 198 CM, 61 NM, and 75 other) for a total of 875 tumors. Median follow-up was 18 months. Complete ablation was confirmed for 839 of 865 tumors (97.0%) on follow-up cross-sectional imaging (Table). NM had greater odds of an incomplete ablation compared to other histologies (odds ratio: 3.07, 95% confidence interval [CI]: 1.08-8.67, p=0.035), however this was not significant in adjusted models. The local recurrence rate was 6.1% overall, and was highest for HCC tumors (10.3%, p=0.051). RFS did not vary significantly between histologies. In adjusted models, tumor size ≥3cm was the only variable predicting poorer RFS (hazard ratio: 1.60, 95% CI: 1.02-2.50, p=0.039). Independent predictors of poorer OS included age, number of tumors ablated, and tumor size ≥3cm. Conclusions: In this large dataset, patients with ≥3cm tumors showed a propensity for early recurrence, regardless of histology. Higher rates of local recurrence were noted in HCC patients, which may reflect underlying liver disease. Accounting for recurrence at any site, however, there were no significant differences in RFS between tumor histologies. [Table: see text]