Magnetic Resonance-Guided Adaptive Radiotherapy for Prostate Cancer: The First Results from the MOMENTUM study, an International Registry for the Evidence-Based Introduction of Magnetic Resonance-Guided Adaptive Radiotherapy.

Magnetic resonance (MR)-guided radiotherapy (MRgRT) is a new technique for treatment of localized prostate cancer (PCa). We report the 12-month outcomes for the first PCa patients treated within an international consortium ([XXXX] study) on a 1.5T MR-Linac system with ultra-hypofractionated radiotherapy.
Patients treated with 5 × 7.25 Gy were identified. Prostate specific antigen (PSA)-level, physician-reported toxicity (Common Terminology Criteria for Adverse Events [CTCAE]), and patient-reported outcomes (PRO) (QLQ-PR25 and QLQ-C30 questionnaires) were recorded at baseline and at 3, 6, and 12 months of follow-up (FU). Pairwise comparative statistics were conducted to compare outcomes between baseline and FU.
Four-hundred-and-twenty-five patients with localized PCa (11.4% low, 82.0% intermediate, and 6.6% high risk) were included, and 365, 313, and 186 patients reached 3, 6, and 12 months FU, respectively. Median PSA level declined significantly to 1.2 ng/mL and 0.1 ng/mL at 12 months FU for the non-ADT and ADT group, respectively. The peak of genitourinary and gastrointestinal CTCAE toxicity was reported at 3 months FU, with 18.7% and 1.7% grade ≥ 2, respectively. The QLQ-PR25 questionnaire outcomes showed significant deterioration in urinary domain score at all FU moments, from 8.3 (IQR: 4.1-16.6) at baseline to 12.4 (IQR: 8.3-24.8; p=0.005) at 3 months, 12.4 (IQR: 8.3-20.8; p=0.018;) at 6 months, and 12.4 (IQR: 8.3-20.8; p=0.001) at 12 months. For the non-ADT group, physician- and patient-reported erectile function worsened significantly between baseline and 12 months FU.
Ultra-hypofractionated MRgRT for localized PCa using a 1.5T MR-Linac is effective and safe. The peak of CTCAE genitourinary and gastrointestinal toxicity was reported at 3 months FU. Furthermore, for patients without ADT, a significant increase in CTCAE erectile dysfunction was reported at 12 months FU. These data are useful for educating patients on expected outcomes and informing study design of future comparative-effectiveness studies.

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