Microvascular Invasion is the Significant Risk Factor in Solitary Hepatocellular Carcinoma Equal or Less than 2cm

Abstract

Introduction: In American Joint Committee on Cancer (AJCC) 8th edition for hepatocellular carcinoma (HCC), stage T1a was redefined as solitary tumor≤2cm irrespective of microvascular invasion(MVI). We investigated the effect of MVI on the disease free (DFS) and overall survival (OS) of small HCC≤2cm, and conducted validation of AJCC 8th edition staging. Method: From January 2000 to December 2020 at Severance Hospital, Seoul, Korea, patients who underwent liver resection and pathologically confirmed with HCC≤2cm were enrolled. The clinicopathologic characteristics, surgical and oncologic outcomes were compared by dividing into two groups according to the MVI. DFS and OS were compared between two groups after propensity score matching (PSM). We evaluated risk factors affecting DFS and OS. Results: Total 265 patients were enrolled and 22 patients of vaguely nodular type were excluded. 156 patients were MVI(-) and 87 patients were MVI(+) and 66 patients of each groups after PSM were compared. Clinicopathologic characteristics did not differ significantly except for poorly differentiated rate in major (MVI-1.5%, MVI+13.6%, p=0.011) and worst differentiation (MVI-31.8%, MVI+57.6%, p<0.001). MVI(+) group showed significantly poor DFS than MVI(-) group(p=0.007), however OS did not show statistical difference (p=0.084). Blood loss more than 150cc (HR: 1.859, p=0.026) and C-viral etiology (HR: 3.485, p=0.001) were significant risk factor for DFS in multivariate analysis. Preoperative platelet count over 150k significantly reduced death rate (HR: 0.430, p=0.049). Conclusions: Microvascular invasion is the significant risk factor for recurrence in small HCC≤2cm. AJCC 8th edition, which underestimated the prognostic effect of MVI in small HCC, should be reevaluated.