Impact of microvascular invasion on clinical outcomes after curative-intent resection for intrahepatic cholangiocarcinoma

Background: Microvascular invasion (MiVI) is a histological feature of intrahepatic cholangiocarcinoma (ICC) that may be associated with biological behavior. We sought to investigate the impact of MiVI on long-term survival of patients undergoing curative-intent resection for ICC. Methods: A total of 1089 patients undergoing curative-intent resection for ICC were identified. Data on clinicopathological characteristics, disease-free survival (DFS), and overall survival (OS) were compared among patients with no vascular invasion (NoVI), MiVI, and macrovascular invasion (MaVI). Results: A total of 249 (22.9%) patients had MiVI, while 149 (13.7%) patients had MaVI (±MiVI). MiVI was associated with higher incidence of perineural, biliary and adjacent organ invasion, and satellite lesions (all P < 0.01). On multivariable analysis, MiVI was an independent risk factor of DFS (hazard ratios [HR] 1.5; 95%confidence intervals [CI], 1.3-1.9; P < 0.001), but not OS (HR 1.1; 95%CI, 0.9-1.3; P = 0.379). While MiVI and MaVI patients had similar DFS (median, MiVI 14.0 vs MaVI 12.0 months, HR 0.9; 95%CI, 0.7-1.2; P = 0.377), OS was better among MiVI patients (median, MiVI 39.0 vs MaVI 21.0 months, HR 0.7; 95%CI, 0.5-0.8; P = 0.002). Whereas nodal metastasis, R1 margin, and postoperative morbidity were associated with early death (≤18 months) among patients with MiVI, only nodal metastasis was associated with late (>18 months) prognosis. Conclusions: Roughly 1 out of 5 patients with resected ICC had MiVI. MiVI was associated with advanced tumor characteristics and a higher risk of tumor recurrence.