Optimising acute toxicity monitoring in prostate MR-guided radiotherapy workflow: Results from a prospective study using multiple electronic PRO assessments.

Introduction: Frequent electronic patient-reported outcomes (ePROs) may become an important tool for monitoring outcomes in ultrahypofractionated MRgRT for prostate cancer, enabling real-time remote tracking of toxicity. By integrating weekly ePROs and health-related quality of life (HRQoL) assessments into the early prostate MRgRT workflow, this study aimed to explore real-time acute symptom trajectories and the impact on HRQoL. Methods: Two cohorts were followed: Patients receiving MRgRT for localised PCa (60Gy/20fx) or low-volume metastatic (M1) PCa (36Gy/6fx) and eligible to complete weekly ePROs and HRQoL measures (EQ-5D-5L, EORTC QLQ-C30) during and up to 24 weeks of follow-up. Linear mixed models were used to evaluate symptom changes over time. Results: Of 76 included PCa patients, 42 had localised PCa and 34 low-volume M1 PCa. The linear model revealed significant changes in urinary symptoms from treatment week one, persisting 2 weeks post-MRgRT in the 36 Gy cohort, and 3-4 weeks in the 60 Gy cohort. Bowel symptoms increased early post-treatment in both cohorts, with diarrhoea being most frequent. Clinically relevant changes in HRQoL were observed during follow-up: patients in the 60 Gy cohort showed HRQoL improvements after 12 and 24 weeks. In the 36 Gy cohort, patients reported improved self-rated Global health status/QoL and emotional functioning. Conclusion: Frequent ePROs during and after MRgRT provide critical insights into the timing, fluctuation and severity of acute toxicity, potentially missed with standard follow-up schedules. Integrating real-time ePROs into the MRgRT workflow is a feasible patient-centered method to systematically optimize the outcome assessments of MRgRT.