Efficacy of Stereotactic Body Radiotherapy (SBRT) Combined With Maintenance Therapy Compared to Maintenance Therapy Alone in Advanced Pancreatic Cancer

Inclusion Criteria:

* Age 18 to 70 years old.
* Histologically or cytologically confirmed diagnosis of pancreatic - adenocarcinoma.
* No prior radiation therapy for pancreatic cancer.
* At least one measurable lesion of the primary pancreatic tumor as per RECIST 1.1 criteria, eligible for SBRT.
* Completion of first-line chemotherapy with stable disease (SD) or partial response (PR) after ≥4 months of treatment.
* ECOG performance status of 0-2.
* Expected survival of ≥3 months.
* Adequate organ function within 14 days prior to enrollment:
* Hemoglobin (Hb) ≥ 90 g/L
* Absolute neutrophil count (ANC) ≥ 1.5×10⁹/L
* Platelets (PLT) ≥ 75×10⁹/L
* Total bilirubin ≤ 1.5× ULN or direct bilirubin ≤ ULN
* ALT/AST ≤ 2.5× ULN
* ALP ≤ 2.5× ULN
* Serum creatinine ≤ 1.5× ULN or calculated creatinine clearance ≥ 40 mL/min
* Urine protein \< 2+ (if ≥2+ on dipstick, 24-hour urine protein must be \< 2g)
* No use of systemic corticosteroids in the last 7 days prior to enrollment (physiological corticosteroid replacement is allowed).
* Women of childbearing potential and men must use effective contraception during the study and for 12 months following treatment completion.
* Voluntary participation with signed informed consent.
* Ability to comply with the study schedule.

Exclusion Criteria:

* Currently participating in any interventional clinical trial or having received other investigational drugs or devices within 4 weeks prior to enrollment.
* Peritoneal metastasis.
* Known active central nervous system (CNS) metastasis and/or carcinomatous meningitis.
* Receiving systemic corticosteroid treatment within 7 days prior to enrollment (except for physiological doses).
* Active, untreated hepatitis B (HBsAg positive and detectable HBV-DNA) or active hepatitis C infection (HCV antibody positive and detectable HCV RNA).
* Pregnant or breastfeeding women.
* Any severe or uncontrolled systemic disease, including:
* QTc interval ≥ 480 ms
* Unstable angina
* NYHA class III-IV congestive heart failure
* Arterial thromboembolism (MI, unstable angina, stroke, TIA) within 6 months prior to enrollment
* Uncontrolled hypertension (systolic BP ≥ 150 mmHg, diastolic BP ≥ 90 mmHg)
* Active pulmonary tuberculosis, severe infections, or other uncontrolled diseases
* Active gastrointestinal perforation, fistula, or bowel obstruction.
* Inadequately controlled diabetes (fasting blood glucose \> 10 mmol/L).
* History of mental illness preventing compliance with treatment.
* Active bleeding or significant coagulation abnormalities within the last 30 days.
* Previous gastrointestinal perforation or other serious gastrointestinal conditions in the past 6 months.
* Participation in other trials that may interfere with this study.