Background: Relugolix, an oral gonadotropin releasing hormone (GnRH) receptor antagonist, was FDA approved for the treatment of adults with advanced prostate cancer (PC) in December 2020 and became commercially available in January 2021. Data from a subgroup of patients from the Phase 3 HERO study showed patients combining relugolix with enzalutamide or docetaxel had similar efficacy and safety as other cohorts in the study. However, due to limited data, some guidelines do not recommend relugolix in combination with other therapies. We evaluated real world utilization of leuprolide and relugolix in combination with other PC medications. Methods: An observational retrospective analysis was conducted using Electronic Medical Record (EMR) data. PPS Analytics data from 89 urology practices with patients represented across all 50 states in the US were analyzed. Patients with at least one record of androgen deprivation therapy (ADT) in 2021 were included. Patients whose date of ADT initiation could not be determined were excluded from this analysis. This analysis focused on the occurrence of patients with ADT as well as in combination with other PC medications. Data are reported for all patients treated with leuprolide or relugolix and stratified by new and continuing ADT use. Combination PC medications were reported for these two ADT groups. Results: In 2021, 51,735 patients were treated with ADT; 45,599 (88.1%) were treated with leuprolide and 3,096 (6.0%) patients had at least 1 prescription for relugolix. Combination PC medications (ComboPCRx) were proportionately higher in relugolix patients than in leuprolide patients (698 [22.5%] vs 8,897 [19.5%] respectively; p < 0.0001). ComboPCRx in users new to ADT was more frequent for relugolix users (342/2,169 [15.8%]) than for leuprolide users (1934/17,737 [10.9%]). In both groups, novel anti-androgens were the most frequent type of ComboPCRx. Conclusions: In this real-world EMR analysis, relugolix use in combination with other PC medication was frequently observed, for both new to ADT and continuing ADT patients. The percentage of combination therapy with PC medications was higher for relugolix users than it was for leuprolide users. These results provide insight into the real-world use of relugolix in combination with other PC medications. Further analyses are needed to make informed treatment decisions.

*Patient can have more than 1 ComboPCRx type.