Efficacy of S-1 Adjuvant Chemotherapy for Resected Biliary Tract Cancer: A Retrospective Propensity-Matched Analysis

Introduction: Surgical resection is considered an effective cure for biliary tract cancer (BTC); however, the prognosis is unsatisfactory despite improved surgical techniques and perioperative management. The recurrence rate remains high even after curative resection. The efficacy of adjuvant chemotherapy in pancreatic and gastric cancers has been previously reported, and the feasibility of adjuvant therapy with S-1 has recently been reported in patients with resected BTC. We aimed to retrospectively investigate the effects of adjuvant chemotherapy with S-1 on resected advanced BTC. Methods: We included data from 438 BTC patients who underwent resection between 2001 and 2020. After excluding patients with pTis-pT1 (n = 112) and other exclusion criteria, 266 patients were included in the analysis. Results: After propensity score matching, 48 patients received S-1 adjuvant chemotherapy (S-1 group), and 48 patients received non-S1 adjuvant chemotherapy or underwent surgery alone (Non-S-1 group). The patients in the S-1 group had significantly better overall survival (OS) than those in the non-S-1 group (MST 51 vs 37 months, hazard ratio [HR]:.54, 95% confidence interval [CI]:.30-.98, P = .04). The S-1 group had a significantly better recurrence-free survival (RFS) than the non-S-1 group (94 vs 21 months, HR: .57, 95% CI: .33-.97, P = .03). Subgroup analyses for OS and RFS exhibited the benefits of S-1 in patients aged <75 years and in patients with primary sites of extrahepatic and perineural invasion and curability of R0. Discussion: S-1 adjuvant therapy is promising for improving the postoperative survival of patients with resected advanced BTC, positive nerve invasion, and R0 resection.