MR-guided SBRT for localized prostate cancer: the first results from the MOMENTUM study

Abstract

Purpose or Objective Magnetic resonance (MR) guided adaptive radiotherapy (MRgRT) is a new technique for treatment of localized prostate cancer (PCa). MR-guided linear accelerator (MR-Linac) systems have been implemented in radiotherapy departments around the world. However, the theoretical benefits of MRgRT still need to be confirmed in clinical practice. We report the short-term outcomes for the first PCa patients treated within an international consortium on a 1.5T MR-Linac system with ultrahypofractionated radiotherapy. Materials and Methods Patients treated with 5x7.25 Gray were identified within the registry. Prostate specific antigen (PSA), Common Terminology Criteria for Adverse events (CTCAE) and patient reported outcome (PRO) using the European Organisation for Research and Treatment of Cancer (EORTC) Quality of Life Questionnaire (QLQ)- PR25, EORTC QLQ-C30 and the EuroQol EQ5D-5L were prospectively recorded at baseline and at 3 and 6 months follow-up (FU). Descriptive and pairwise comparative statistics were conducted. Results One-hundred-and-fifty-six consecutive patients with localized PCa (13.2% low-, 77.2% intermediate-, and 9.6% high-risk [National Comprehensive Cancer Network risk groups]) were included. Thirty-one patients (19.9%) received neoadjuvant androgen deprivation therapy (ADT). A significant decline of PSA in non-ADT patients was observed between baseline (median: 7.8 ng/mL), 3 months FU (median: 2.7 ng/mL) and 6 months FU (median: 1.7 ng/mL) (p<0.001). No grade ≥3 genitourinary (GU) or gastrointestinal (GI) toxicity was reported (table). No significant deterioration of PRO scores were observed. The percentage of men reporting no difficulty getting or maintaining an erection remained constant throughout FU (44.4% at baseline, 40.0% at 3 months FU, and 42.9% at 6 months FU). The highest grade of a given toxicity that occurred in a time period (3 months FU=0 to 3 months after treatment; 6 months FU=3 to 6 months after treatment). Data available: baseline=68/156 patients; 3 months FU=39/147 patients; 6 months FU=20/124 patients Conclusion Ultrahypofractionated 1.5T MR-Linac treatment of localized PCa is effective and safe (no grade ≥3 GU or GI toxicity). In the first 6 months following treatment, patients reported stable erectile function. No significant deterioration of PROs at 3- and 6-months FU was observed.