This prospective real-world study aims to evaluate the effectiveness and safety of an alternating treatment regimen combining hepatic arterial infusion chemotherapy (HAIC) with systemic chemotherapy, with or without adebrelimab and apatinib, in patients with unresectable biliary tract cancer receiving first-line treatment. The study comprises two cohorts: one receiving alternating HAIC and systemic chemotherapy alongside adebrelimab and apatinib, and the other receiving alternating HAIC and systemic chemotherapy alone. Treatment allocation follows real-world clinical decision-making. Patients will be monitored throughout the treatment period to assess tumor response, survival outcomes, and safety profiles. The study aims to generate evidence on the clinical benefits of integrating immunotherapy and targeted therapy into HAIC-based regimens for this patient population.

Biliary tract cancer (BTC), which includes intrahepatic cholangiocarcinoma, extrahepatic cholangiocarcinoma, and gallbladder cancer, is an aggressive malignancy associated with a generally poor prognosis. For patients with unresectable, locally advanced, or metastatic disease, first-line systemic chemotherapy using gemcitabine and cisplatin remains the standard of care, although treatment outcomes are ofter suboptimal. HAIC has gained increasing attention in clinical practice, paticularly in China, for its ability to enhance local drug delivery and improve tumor control in cases of liver-dominant disease. Alternating HAIC with systemic chemotherapy may provide additive benefits by simultaneously targeting both intrahepatic and extrahepatic lesions.

Recent advances in immunotherapy and anti-angiogenic therapy have shown promise results in BTC. Adebrelimab, a PD-L1 inhibitor, and apatinib, a VEGFR2 inhibitor, have demonstrated antitumor activity in various solid tumors. Combining these agents with chemotherapy and HAIC may yield synergistic effects, potentially improving response rates and extending survival.

This prospective real-world study is designed to evaluate the effectiveness and safety of an alternating regimen of HAIC and systemic chemotherapy (gemcitabine plus cisplatin), with or without adebrelimab and apatinib, in patients with previously untreated, unresectable, locally advanced or metastatic BTC. Participants will be assigned to one of two cohorts based on patient preference and clinician judgment: Cohort A will receive HAIC and systemic chemotherapy combined with adebrelimab and apatinib, while Cohort B will receive HAIC and systemic chemotherapy alone. Dosing and administration will follow the standard treatment protocols.

The study will capture real-world data on objective tumor response, progression-free survival, overall survival, and safety profiles. Exploratory analyses may include patterns of disease progression, treatment adherence, and the influence of clinical and biological factors on outcomes. The results are anticipated to offer valuable evidence to guide clinical decision-making and help optimize first-line treatment strategies for patients with advanced BTC in routine practice.

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.