Real-world use of olaparib in US veterans with metastatic castration-resistant prostate cancer: Treatment patterns and outcomes.

5071 Background: Olaparib, a targeted therapy for metastatic castration-resistant prostate cancer (mCRPC), has demonstrated clinical benefits in patients with homologous recombination repair (HRR) gene alterations, as shown in the PROfound trial. As the largest integrated healthcare system in the US, the Veteran’s Health Administration (VHA) offers insights into olaparib use among a diverse population. We characterized the treatment patterns and outcomes of patients with mCRPC treated with olaparib. Methods: We identified all VHA patients with mCRPC who received olaparib between May 2020 and December 2023. We then performed a retrospective chart review of data from May 2018 to June 2025 to capture pre- and post-treatment data. Demographics, baseline characteristics, biomarker testing and treatment sequencing were summarized. We analyzed time to event outcomes: time to next therapy (TTNT), and overall survival (OS) via Kaplan-Meier methods, both starting from olaparib initiation. Results: We identified 477 mCRPC patients receiving olaparib. Median age at initiation was 75, older than subjects in PROfound (median age 69). Most patients were non-Hispanic White (69%), followed by Black/African American (20%) and Hispanic/Latino (6%). Between 2020 and 2023, olaparib was most commonly initiated in ≥5th line after prostate cancer diagnosis (46%), followed by 4 th (25%), 3 rd (22%), and 2 nd line (6.5%). All patients had received an androgen receptor pathway inhibitor prior to olaparib. Median time from HRR testing to olaparib initiation was 5 months. Median TTNT was 7 months; OS was 12 months. Use of olaparib in an earlier line post first NHA was associated with numerically longer OS (17 months for 1st line vs. 8 months for 4th or later). Conclusions: Within the VHA, olaparib showed favorable outcomes despite older age and late-line use, supporting effectiveness in routine practice and in a more diverse population with substantially higher representation of Black/African American and Hispanic/Latino individuals than in clinical trials. Understanding these treatment patterns provides insight into clinical practice and helps guide towards optimal integration of olaparib into management of mCRPC. Kaplan-Meier estimates for time to event outcomes. #Events/Total Median Time (95% CI) (months) Time to Next Treatment - All Patients 449/477 7 (6-8) - Olaparib Line of Treatment Post NHA 1st line 100/111 9 (7-10) 2nd line 151/162 8 (7-10) 3rd line 92/96 6 (5-8) 4th line or later 91/92 5 (4-6) Overall Survival - All Patients 395/477 12 (11-13) - Olaparib Line of Treatment Post NHA 1st line 79/111 17 (12-22) 2nd line 133/162 15 (12-17) 3rd line 85/96 10 (8-12) 4th line or later 88/92 8 (6-9)