Background: Relugolix, an oral gonadotropin releasing hormone (GnRH) antagonist, has superior testosterone suppression and may lower cardiovascular (CV) toxicity compared with more commonly used injectable GnRH agonists, such as leuprolide. The Relugolix Versus Leuprolide Trial (REVELUTION, NCT 05320406) is an ongoing, investigator-initiated, randomized trial comparing radiotherapy (XRT) plus relugolix versus XRT plus leuprolide for men with localized prostate cancer (PCa). Primary endpoint is change in coronary plaque on cardiac computed tomography from baseline to 12 months following treatment. Secondary endpoints include patient-reported outcomes (PRO). Herein, we report patient-specific treatment preferences prior to randomization and acute treatment-associated toxicity. Methods: Men with non-metastatic intact or biochemically recurrent PCa pursuing pelvic XRT (1.8-2.5 Gy per fraction) with ≥ 6 months of androgen deprivation therapy (ADT) were enrolled and randomized 1:1 to leuprolide (IM/SC 45 mg q6mo) or relugolix (PO 360 mg day 1, 120 mg daily thereafter). Prior to randomization, each patient completed an ADT preference questionnaire after reviewing an education brochure describing both drugs’ administration, testosterone kinetics, and common toxicities. PROs were assessed by International Prostate Symptom Score (IPSS) and Expanded Prostate Index Composite (EPIC-CP) at baseline and 3-/6-months after XRT initiation, with higher scores indicating more severe toxicity. Scores were compared using linear mixed-effects models accounting for within-subject correlations. Results: Between 06/2022 and 07/2023, 65 men were randomized (34 leuprolide, 31 relugolix). Median follow-up was 5 months (IQR 4-8). Prior to randomization, 61 (94%) preferred relugolix over leuprolide, due to faster testosterone recovery (n=36, 59%), lower CV risk (n=23, 38%), or oral administration (n=2, 3%); the four patients who preferred leuprolide all had compliance concerns with a daily oral pill. Compared with XRT+leuprolide, XRT+relugolix was associated with less impact on IPSS urinary score (mean difference [MD] -3.68, p=0.04). There was no difference in EPIC-CP incontinence (MD +0.07, p=0.91), bowel (MD +0.39, p=0.44), sexual (MD -0.74, p=0.43), or vitality (MD +0.17, p=0.80). Conclusions: In this trial of men with localized PCa treated with XRT plus ADT, most preferred relugolix over leuprolide. Relugolix, compared with leuprolide, mitigated acute urinary toxicity from XRT, perhaps due to superior castration resulting in greater prostate gland downsizing and less obstructive uropathy. Longer-term follow up is ongoing, and primary CV toxicity endpoint is expected to be complete in 2024. Clinical trial information: NCT05320406.