Real-World Outcomes of Olaparib Treatment in Japanese Patients With Metastatic Castration-Resistant Prostate Cancer Harboring BRCA Pathogenic or Likely Pathogenic Variants.

Olaparib has demonstrated clinical benefit in patients with metastatic castration-resistant prostate cancer (mCRPC) harboring BRCA pathogenic or likely pathogenic variants (PVs) in randomized clinical trials; however, multicenter real-world data in Japanese patients remain limited. This multicenter retrospective study included Japanese patients with mCRPC who received olaparib between 2021 and 2025 at four institutions. Eligible patients had pathogenic or likely pathogenic BRCA1/2 variants identified by comprehensive genomic profiling or BRCA-specific testing (BRACAnalysis). Disease progression was defined as prostate-specific antigen (PSA) progression or radiographic progression. Overall survival (OS) and progression-free survival (PFS) were estimated using the Kaplan-Meier method. Among 128 patients undergoing comprehensive genomic profiling, 18 (14%) were identified as having BRCA PVs, of whom 13 received olaparib. Among 239 patients tested by BRACAnalysis, 14 (6%) harbored BRCA PVs and all received olaparib. Overall, 27 patients with mCRPC harboring BRCA PVs were analyzed. The median duration of olaparib treatment was 8 months, with three patients treated for more than 30 months. One-year OS rate was 80.6%, with a median OS of 18.4 months, and 1-year PFS rate was 27.2% with a median PFS of 7.6 months. Grade 3 anemia occurred in 33% of patients and was manageable, with no grade 4 or 5 events observed. This multicenter retrospective study provides real-world data on olaparib treatment in Japanese patients with mCRPC harboring BRCA PVs. The observed outcomes and safety profile were generally consistent with previous reports, although interpretation is limited by the small sample size, retrospective design, and heterogeneity of prior treatments.