Liposomal Irinotecan Plus 5-FU/LV and Sintilimab With Sequential SBRT for Locally Advanced Biliary Tract Cancer

This is a prospective, single-arm, exploratory interventional study designed to evaluate the efficacy and safety of liposomal irinotecan (II) plus fluorouracil/leucovorin (5-FU/LV) and sintilimab with sequential stereotactic body radiation therapy (SBRT) as first-line treatment for patients with unresectable locally advanced biliary tract cancer (BTC) who have not received prior systemic anticancer therapy for their current disease. Approximately 31 participants will be enrolled. Participants will receive liposomal irinotecan (II), 5-FU/LV, and sintilimab. Participants without disease progression after initial systemic treatment will receive sequential SBRT to the primary biliary tract tumor. After eight administrations of chemotherapy (approximately 16 weeks), resectability will be assessed by a multidisciplinary team. Participants considered eligible for surgery will undergo radical surgical resection followed by adjuvant treatment, whereas those who remain unresectable will continue the study treatment until disease progression or another protocol-defined reason for discontinuation. The primary endpoint is objective response rate (ORR) according to Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1. Secondary endpoints include disease control rate (DCR), progression-free survival (PFS), overall survival (OS), surgical conversion rate (SCR), and safety.