NALIRIFOX+Adebrelimab+PULSAR for Advanced Pancreatic Cancer

Inclusion Criteria: * Age: 18-75 years, regardless of gender. * Histologically confirmed pancreatic ductal adenocarcinoma (PDAC). * Previously untreated, locally advanced unresectable or metastatic PDAC, with at least one measurable lesion (RECIST v1.1) not previously irradiated. * ECOG Performance Status (PS): 0-1. * Expected survival ≥ 3 months. * Willing and able to comply with study procedures, treatment, and follow-up. * No contraindications to radiotherapy. * Adequate organ function: WBC ≥ 2.5×10⁹/L, ANC ≥ 1.5×10⁹/L; Platelets ≥ 75×10⁹/L; Hemoglobin (HGB) ≥ 90 g/L (no transfusion or EPO dependence within 7 days); Total bilirubin (Tbil) ≤ 1.5×ULN; ALT/AST ≤ 5×ULN;Albumin ≥ 30 g/L; INR ≤ 1.5×ULN; Serum creatinine (Cr) ≤ 1.5×ULN Urine protein ≤ 1+ * HBsAg-positive patients must have HBV-DNA ≤ 1×10³ IU/mL (copies/mL). If HBV-DNA ≥ 1×10³ IU/mL, patients may still be eligible if chronic HBV is stable and not expected to increase risk, per investigator assessment. * Voluntary participation with signed informed consent form. Exclusion Criteria: * History of severe hypersensitivity to chimeric, human(ized) antibodies, or fusion proteins. * Pregnant or breastfeeding women, or men/women of childbearing potential unwilling/unable to use effective contraception during the study. * Other malignancies within 5 years, except: Malignancies treated with curative intent and no known active disease for ≥5 years with low recurrence risk; Adequately treated non-melanoma skin cancer or lentigo maligna without disease evidence; Adequately treated carcinoma in situ (e.g., cervical, breast) with no current disease. * Symptomatic moderate/severe pleural effusion or ascites. * Active bleeding or coagulopathy (PT \>16s, APTT \>43s, INR \>1.5×ULN), bleeding tendency, or current use of thrombolytics/anticoagulants/antiplatelets. * GI bleeding within 6 months or high bleeding risk (e.g., active ulcer with occult blood++). If occult blood+ persists, endoscopy required. * High-risk esophageal/gastric varices needing intervention. * History of drug abuse, psychiatric disorder, or inability to abstain. * Solid organ/bone marrow transplant, or active autoimmune disease requiring systemic treatment within 2 years. * Immunodeficiency or HIV infection. * Objective evidence of pulmonary fibrosis, interstitial lung disease, pneumoconiosis, radiation-/drug-induced pneumonitis, or severely impaired pulmonary function. * Major surgery within 4 weeks or minor surgery within 1 week (e.g., tooth extraction). * Vaccination within 30 days before the first dose. * Abdominal fistula, GI perforation, or abscess within 4 weeks. * Any clinically significant abnormality affecting safety per investigator, including: Active infection requiring systemic therapy; Uncontrolled diabetes/hypertension (BP \>140/90 mmHg despite ≤2 antihypertensives); Myocardial infarction within 6 months; Thyroid dysfunction (\>NCI CTCAE v4.0 Grade 1). * Other conditions deemed ineligible by the investigator.