Magnetic resonance-guided online adaptive stereotactic body radiotherapy for advanced inoperable pancreatic cancer: a prospective study

To assess the local control, safety, and symptom relief of magnetic resonance-guided online adaptive stereotactic body radiation therapy (MRg-oART-SBRT) combined with systemic therapy in advanced unresectable pancreatic cancer. This single-center, open-label, prospective trial enrolled ≥ 18-year-old patients with pathologically confirmed pancreatic ductal adenocarcinoma, including locally advanced, post-recurrent, and oligometastatic cases deemed unresectable via multidisciplinary evaluation. ECOG 0–2 patients with/without prior chemotherapy received 40–50 Gy/5 fractions via 1.5T MR-linear accelerator with daily online adaptive radiotherapy. Primary endpoint was 6-month local control rate; secondary endpoints included 3-month pain relief, ≥G3 gastrointestinal toxicity within 90 days, and 6-month distant progression-free survival. From November 2023 to December 2024, 34 patients completed MRg-oART-SBRT. With median follow-up of 12.3 months (IQR 9.0–14.4) after radiotherapy, the 6-month and 1-year local control rate were both 80.2%. Median distant progression-free survival was 9.7 months after radiotherapy. 97% reported pain relief at 3 months after radiotherapy. Acute probably radiation-related toxicity was mild (G1–2 diarrhea 18%). Thrombocytopenia (G2–3: 18%) and palmar-plantar erythrodysesthesia (G1–2: 12%) were most common treatment-related adverse reactions. MRg-oART-SBRT demonstrates encouraging short-term control, manageable toxicity, and survival signals in advanced pancreatic cancer. Larger multicenter trials with extended follow-up are warranted to validate long-term efficacy and clinical utility. The study was registered on the Chinese Clinical Trial Registry, with the registration number ChiCTR2500096492.The retrospective registration date was January 24, 2025.