Risk factors for shorter recurrence-free survival in patients with resected biliary tract cancer treated with adjuvant S-1 chemotherapy

Abstract Background Adjuvant S-1 chemotherapy (ASC) has become the standard postoperative treatment for biliary tract cancer (BTC) in Japan following publication of the results of the ASCOT study, a recent nationwide randomized controlled study. However, recurrence remains common, and risk factors specific to patients treated with ASC are unclear. Methods We retrospectively investigated the data of 56 patients with resected BTC at our institution between August 2021 and October 2023. Recurrence-free survival (RFS), overall survival (OS), and treatment safety were evaluated. Cox proportional hazards regression analysis was performed to identify the risk factors for shorter RFS. Results Over a median follow-up of 22.6 months, 15 patients (26.8%) developed recurrence. The 12- and 24-month RFS rates were 84.8% and 71.6%, respectively, and the 12- and 24-month OS rates were 92.4% and 85.7%, respectively. Both univariate and multivariate analyses identified poorly differentiated tumor histology as a significant risk factor for shorter RFS. In addition, univariate analysis, but not multivariate analysis, also identified elevated pre-ASC serum CA19-9 levels (≥ 37 U/mL) as a significant risk factor for shorter RFS. Adverse events of ≥ grade 3 occurred in 3.6% of patients receiving ASC. Conclusions Poorly differentiated tumor histology may be a risk factor for shorter RFS in patients with resected BTC treated with ASC.