Olaparib for Chinese Metastatic Castration-resistant Prostate Cancer: A Real-World Study of Efficacy and Gene Predictive Analysis

Abstract Objective: To evaluate the real-world effectiveness and gene predictive analysis of olaparib in Chinese patients with metastatic castration-resistant prostate cancer (mCRPC) .Methods: A multicenter, retrospective, real-world study was conducted by involving Chinese patients with mCRPC from December 2017 to June 2021. Homologous Recombination repair (HRR)gene mutation (HRRm) status was identified using targeted next-generation sequencing (NGS). The primary endpoint includes prostate-specific antigen (PSA) response rate (PSA50). Secondary end points include PSA progression-free survival (PSA-PFS), exploratory endpoints include PSA50, and PSA-PFS in HRRm-negative patients with variants of unknown significance (VUS). Survival rates were analyzed using Kaplan–Meier (KM) plot.Results: A total of 39 eligible patients with a median age of 65 (interquartile range [IQR]: 59.5-69.5) years were included in the study. Overall, 40% (12/30) of the patients with mCRPC achieved PSA50 and the median PSA-PFS was 3.1 months (95% Confidence interval [CI]: 2.4-7). Furthermore, higher PSA50 rate and longer PSA-PFS were observed in HRRm-positive patients (PSA50: 50% [7/14]; median PSA-PFS: 5.3 months, 95% CI: 3.73–10). Among the HRRm-positive patients, those harboring the BRCA2 aberrations experienced best clinical efficacy (PSA50: 55.5% [5/9] and median PSA-PFS [95% CI]: 9.5 months [4.3, NA]). Clinical benefit was also observed in HRRm-negative patients (PSA50: 31.3% [5/16]; median PSA-PFS [95% CI]:2.05 months [1.5,8]), wherein most patients with a PSA50 response were carrying VUS mutations (PSA50: 50% [4/8]; median PSA-PFS [95% CI]: 2.75 months [1.27, NA]). In one patients with mutation in the ATR gene, the PSA level decreased by 62%. Conclusion: Olaparib improved PSA response and prolonged PSA-PFS in Chinese mCRPC patients especially in those carrying HRR mutation. Among the HRR genes, patients with BRCA2 mutation showed the best clinical benefit. Besides, some patients carrying HRR VUS alternations and other DNA damage response (DDR) gene mutations also showed response to olaparib treatment, indicating that the clinical benefits observed in HRR negative group were driven by VUS and other DDR gene mutation. However, this should be further explored in the future, and more molecular functional studies are needed to reclassify VUS mutations for better clinical treatment decision-making and management of mCRPC.