Alternating HAIC and Systemic Chemotherapy With or Without Adebrelimab and Apatinib for Unresectable Biliary Tract Cancer

Inclusion Criteria: 1. Age ≥ 18 years at the time of enrollment. 2. Histologically or cytologically confirmed diagnosis unresectable, locally advanced, or metastatic BTC, including intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, and gallbladder cancer. 3. No prior systemic therapy for BTC, including chemotherapy, immunotherapy, or small-molecule targeted therapy. 4. Patients with disease recurrence ≥6 months after curative resection and completion of adjuvant therapy (chemotherapy or radiotherapy) are eligible. 5. Adequate liver function: defined as Child-Pugh Class A (score 5-6) or well-compensated Class B (score ≤7). 6. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1. 7. At least one measurable lesion as defined by RECIST 1.1. 8. Assessed by the investigator as being able to tolerate and comply with the study treatment regimen. 9. Provision of written informed consent, voluntarily agreeing to participate after full explanation of the study protocol. Exclusion Criteria: 1. Hepatic tumor burden occupying ≥50% of total liver volume. 2. History of liver transplantation. 3. Major surgery or invasive procedure (excluding intravenous catheter placement or percutaneous drainage) within 4 weeks prior to enrollment. 4. History or evidence of clinically significant bleeding, including: bleeding \>30 mL within 3 months prior to enrollment (including hematemesis, melena, or hematochezia), hemoptysis (\>5 mL of fresh blood) within 4 weeks prior to enrollment, or thromboembolic events (including stroke or transient ischemic attack) within the past 12 months. 5. Known active infection with human immunodeficiency virus (HIV). 6. Pregnant (a positive pregnancy test prior to study drug administration) or breastfeeding women. 7. Any condition, in the investigator's judgment, that could compromise patient satety, affect the assessment of study outcomes, or lead to premature discontinuation. this includes, but is not limited to: active alcohol or substance abuse, severe uncontrolled comorbidities, significant laboratory abnormalities, or social/family circumstances that could interfere with protocol compliance.