Validation of the Prognostic Role for Surgical Treatment in Stage II Intrahepatic Cholangiocarcinoma: A SEER Population-Based Study.

Background: This study aimed to determine the role of surgical treatment in patients with stage II intrahepatic cholangiocarcinoma (iCCA). Methods: Data were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. We divided stage II iCCAs into solitary tumors with vascular invasion (T2sN0M0) and multiple tumors with/without vascular invasion (T2mN0M0) according to the criteria of AJCC v.8. The Kaplan−Meier method and log-rank test were used to evaluate differences in overall survival (OS). We performed two propensity score-matching analyses with (PSM2) or without (PSM1) surgical treatment. Results: 667 and 778 iCCA patients with stage II and IIIB were recruited. After PSM2, there was no survival difference in stage II iCCA patients in hypothetical conditions with similar surgical proportions (p = 0.079). However, OS was significantly worse in patients with T2mN0M0 than T2sN0M0 when the actual surgical proportion existed after PSM1 (p < 0.001). OS was similar between T2mN0M0 and IIIB regardless of whether PSM1 (p = 0.907) or PSM2 (p = 0.699) was performed. The surgical treatment was verified to associate with prognosis. Conclusions: The survival benefit by surgical treatment was existed in Stage II but not in Stage IIIB iCCA patients. The OS for T2mN0M0 will approach that of T2sN0M0 if the surgical proportion is gradually increased.