ESTRO 2021 Abstract Book

S1009

ESTRO 2021

Conclusion Online adaptive MR-guided SBRT on a 1.5T MR-linac is feasible in patients with unresectable malignancies in the upper abdomen. Dose escalation studies, followed by comparative studies, are needed to determine the optimal radiation dose needed. PO-1219 Utility of MRI-guided adaptive radiotherapy for pancreatic cancer: Baskent University experience G. Yavas 1 , C. Yavas 1 , G. Arslan 2 , E. Efe 3 , C. Onal 3,4 1 Başkent University, Radiation Oncology, Ankara, Turkey; 2 Başkent University , Radiation Oncology, Ankara, Turkey; 3 Başkent University , Radiation Oncology, Ankara, Turkey; 4 Başkent University, Adana Dr Turgut Noyan Research and Treatment Centre, Radiation Oncology, Adana, Turkey Purpose or Objective Pancreatic cancer has been a devastating malignancy, and isolated loco-regional relapses occur in 30% of patients. Novel multidrug combinations have improved clinical outcome in metastatic setting, and are now increasingly being incorporated into the locally advanced/localized settings. 1.5 Tesla magnetic resonance imaging-guided adaptive radiotherapy (MRI-g-ART) allows dose escalation for tumor while minimizing the doses received by healthy tissues due to its higher image quality. Materials and Methods Five patients with inoperable/borderline resectable pancreatic cancer treated with 1.5T MRI-g-ART (Unity® MR Linac System, Elekta AB, Stockholm, Sweden) retrospectively evaluated. Treatment details and early treatment results were reported. Results Three out of five cases were diagnosed as inoperable pancreatic cancer, and received MRI-g-ART for definitive purpose. One of cases received salvage re-irradiation, and other had borderline resectable pancreatic cancer treated preoperatively. The median age of patients was 67 years (range: 62-73 years), and median treatment duration was 53 minutes (range: 33-67 minutes). Local control was achieved in all of cases. Complete pain relief was achieved in one of the patient with inoperable pancreatic cancer suffering from severe pain. One of the cases with locally advanced7unresectable pancreatic cancer had a complete response in primary disease located in pancreatic head. Two of patients had grade 1 gastrointestinal system toxicity. No grade 2 or higher acute toxicity Conclusion MR-g-ART has a promising resource with lower toxicity rates for borderline resectable/unresectable pancreatic cancer, as it allows to modify treatment planning and dose distribution with respect to daily anatomy of the patient.