Adjuvant sintilimab plus capecitabine in resected extrahepatic cholangiocarcinoma: Interim report of a single-arm, prospective phase II study.

557 Background: The efficacy of adjuvant chemotherapy alone in extrahepatic cholangiocarcinoma (EHC) remains limited, with high recurrence rates after resection. This phase II study aimed to assess the safety and efficacy of sintilimab, an anti-PD-1 antibody, in combination with capecitabine as adjuvant therapy for patients with resected ECC. Methods: Eligible patients were aged 18 to 75 years, had histologically confirmed primary EHC, underwent R0 (no local residual tumor) or R1 (microscopic residual tumor) resection and an ECOG performance status score of 0 or 1. Participants received sintilimab (200 mg IV Q3W for 6 cycles) plus capecitabine (1250 mg/m² orally twice daily, days 1–14, Q3W for 8 cycles). The primary endpoint was 2-year recurrence-free survival (RFS). Secondary endpoints included 1-year RFS, 2- and 3-year overall survival (OS), and safety. ClinicalTrials.gov identifier: NCT05207735. Results: As of June 2025, 31 patients were enrolled and received at least one treatment cycle; 23 completed full treatment. Of 31 included patients, 12 (38.7%) were female, and the median age was 62.5 years. Most patients (26 of 31 83.9%) received R0 resection. With a median follow-up of 20.0 months (range:5.8-51.8), the 2-year RFS was 72.8%. The 2-year and 3-year OS rates were 75.5% and 68%, respectively. Further, treatment-related adverse events (TRAEs) of any grade occurred in 74.2% of patients, including anorexia (41.9%), fatigue (25.8%), nausea/vomiting (22.6%), hand-foot syndrome (22.6%), and rash (19.4%). Grade ≥3 TRAEs were observed in 16.1% of patients. No treatment-related deaths were reported. Conclusions: The combination of sintilimab and capecitabine as adjuvant therapy showed promising efficacy and a manageable safety profile in patients with resected EHC, supporting further investigation in randomized trials. Clinical trial information: NCT05207735 .