1.5T Magnetic Resonance-Guided Stereotactic Body Radiotherapy for Localized Prostate Cancer: Preliminary Clinical Results of Clinician- and Patient-Reported Outcomes

Poon, Darren M. C.; Yuan, Jing; Wong, Oi-Lei; Yang, Bin; Chiu, Sin-Ting; Cheung, Kin-Yin; Chiu, George; Yu, Siu-Ki

SIMPLE SUMMARY: The combination of stereotactic body radiotherapy (SBRT) and magnetic resonance-guided radiation therapy (MRgRT) offers the potential for achieving better tumor control and lower toxicities for prostate cancer (PC) patients. This study reports for the first time preliminary longitudinal clinical results of 1.5T MR-guided SBRT (MRgSBRT) in a cohort of 51 localized PC patients (median follow-up: 199 days; range: 41–424 days), based on both clinician-reported outcome measurement (CROM) and patient-reported outcome measurement (PROM). The maximum cumulative clinician-reported grade ≥ 2 (Common Terminology Criteria for Adverse Events Scale v. 5.0) acute genitourinary (GU) and gastrointestinal (GI) toxicities were 11.8% (6/51) and 2.0% (1/51), respectively, while grade ≥ 2 subacute GU and GI toxicities were 2.3% (1/43) each. Patient-reported urinary, bowel, and hormonal domain summary scores were reduced at 1 month, then gradually returned to baseline levels, with the exception of the sexual domain. The finding of low toxicity supports the accumulation of clinical evidence for 1.5T MRgSBRT in localized PC. ABSTRACT: Background: Magnetic resonance-guided stereotactic body radiotherapy (MRgSBRT) offers the potential for achieving better prostate cancer (PC) treatment outcomes. This study reports the preliminary clinical results of 1.5T MRgSBRT in localized PC, based on both clinician-reported outcome measurement (CROM) and patient-reported outcome measurement (PROM). Methods: Fifty-one consecutive localized PC patients were prospectively enrolled with a median follow-up of 199 days. MRgSBRT was delivered in five fractions of 7.25–8 Gy with daily online adaptation. Clinician-reported gastrointestinal (GI) and genitourinary (GU) adverse events based on the Common Terminology Criteria for Adverse Events (CTCAE) Scale v. 5.0 were assessed. The Expanded Prostate Cancer Index Composite Questionnaire was collected at baseline, 1 month, and every 3 months thereafter. Serial prostate-specific antigen measurements were longitudinally recorded. Results: The maximum cumulative clinician-reported grade ≥ 2 acute GU and GI toxicities were 11.8% (6/51) and 2.0% (1/51), respectively, while grade ≥ 2 subacute GU and GI toxicities were 2.3% (1/43) each. Patient-reported urinary, bowel, and hormonal domain summary scores were reduced at 1 month, then gradually returned to baseline levels, with the exception of the sexual domain. Domain-specific subscale scores showed similar longitudinal changes. All patients had early post-MRgSBRT biochemical responses. Conclusions: The finding of low toxicity supports the accumulation of clinical evidence for 1.5T MRgSBRT in localized PC.