ESTRO 2023 - Abstract Book

S1115

Digital Posters

ESTRO 2023

Online adaptive magnetic resonance-guided radiotherapy (MRgRT) is a promising treatment modality for pancreatic cancer and is being employed by an increasing number of centers worldwide. However, clinical outcomes have only been reported on a small scale, often from single institutes and in the context of clinical trials, in which strict patient selection might limit generalizability of outcomes. This study presents clinical outcomes of a large, international cohort of patients with (peri)pancreatic tumors treated with online adaptive MRgRT. Materials and Methods We evaluated clinical outcomes of patients with (peri-)pancreatic tumors treated on a 1.5 Tesla (T) MR-linac in two large volume treatment centers participating in the prospective MOMENTUM cohort (NCT04075305). Patient and treatment details were summarized. Acute toxicity was assessed until three months after start MRgRT, and late toxicity from three to twelve months. The EORTC QLQ-C30, and PAN26 questionnaires were used to evaluate the quality of life (QoL). Treatment response was assessed at three months FU with the RECIST criteria. Furthermore, cumulative overall survival was evaluated using Kaplan-Meier curves. Results A total of eighty patients were assessed with a median follow-up (FU) of 8 months (range 1 to 39 months). Thirty-four patients had an unresectable primary tumor or were medically inoperable, twenty-nine had an isolated local recurrence, and seventeen had an oligometastasis. Out of 358 planned fractions, 357 were delivered as planned for hypofractionated schemes. Grade 3 acute toxicity occurred in three patients (5%) with hypofractionated MRgRT, and grade 3-4 late toxicity in five patients (12%). Six patients (8%) died within three months after MRgRT; in one of these patients, RT attribution could not be ruled out as cause of death. The QLQ-C30 global health status remained stable from baseline to three months FU (70.5 at baseline, median change of +2.7 [P = 0.5]). At three months FU, at least 35 patients (53%) did not show progressive disease, and five (8%) had local progression. The one-year cumulative overall survival for the entire cohort was 67%.