Overall tumor burden dictates outcomes for patients undergoing resection of multinodular hepatocellular carcinoma beyond the Milan criteria

Objective: The objective of the current study was to define surgical outcomes after resection of multinodular hepatocellular carcinoma (HCC) beyond the Milan criteria, and develop a prediction tool to identify which patients likely benefit the most from resection. Background: Liver resection for multinodular HCC, especially beyond the Milan criteria, remains controversial. Rigorous selection of the best candidates for resection is essential to achieve optimal outcomes after liver resection of advanced tumors. Methods: Patients who underwent resection for HCC between 2000 and 2017 were identified from an international multi-institutional database. Patients were categorized according to Milan criteria status. Pre- and postoperative overall survival (OS) prediction models that included HCC tumor burden score (TBS) among patients with multinodular HCC beyond Milan criteria were developed and validated. Results: Among 1037 patients who underwent resection for HCC, 164 (15.8%) had multinodular HCC beyond the Milan criteria. Among patients with multinodular HCC, 25 (15.2%) patients experienced a serious complication and 90-day mortality was 3.7% (n = 6). Five-year OS after resection of multinodular HCC beyond Milan criteria was 52.8%. A preoperative TBS-based model (5-year OS: low-risk, 73.7% vs intermediate-risk, 45.1% vs high-risk, 13.1%), and postoperative TBS-based model (5-year OS: low-risk, 80.1% vs intermediate-risk, 37.2% vs high-risk, not reached) categorized patients into distinct prognostic groups relative to long-term prognosis (both P < 0.001). Pre- and postoperative models could accurately stratify OS in an external validation cohort (5-year OS; low vs medium vs high risk; pre: 66.3% vs 25.2% vs not reached, P = 0.012; post: 61.4% vs 42.5% vs not reached, P = 0.045) Predictive accuracy of the pre- and postoperative models was good in the training (c-index; pre: 0.68; post: 0.71), internal validation (n = 2000 resamples) (c-index, pre: 0.70; post: 0.72) and external validation (c-index, pre: 0.67; post 0.68) datasets. TBS alone could stratify patients relative to 5-year OS after resection of multinodular HCC beyond Milan criteria (c-index: 0.65; 5-year OS; low TBS: 70.2% vs medium TBS: 54.7% vs high TBS: 16.7%; P < 0.001). The vast majority of patients with low and intermediate TBS were deemed low or medium risk based on both the preoperative (98.4%) and postoperative risk scores (95.3%). Conclusion: Prognosis of patients with multinodular HCC was largely dependent on overall tumor burden. Liver resection should be considered among patients with multinodular HCC beyond the Milan criteria who have a low- or intermediate-TBS.