Centralized Homologous Recombination Repair Testing in Metastatic Castration-Resistant Prostate Cancer: Real-World...

Background/Objectives: Determining homologous recombination repair (HRR) status in metastatic castration-resistant prostate cancer (mCRPC) is essential to ensure access to targeted therapies, particularly PARP inhibitors. Yet, variability in testing access and analysis performance exists. This study evaluated feasibility and outcomes of a centralized HRR testing strategy in Spain for prostate cancer patients. Methods: A total of 1412 formalin-fixed paraffin-embedded (FFPE) tumor samples from mCRPC patients from 89 Spanish institutions within a centralized multicenter molecular testing program were analyzed using a standardized 38-gene-based next-generation sequencing (NGS) assay in a central laboratory (HRR OncoKit, Health in Code, Valencia, Spain), which included five clinically relevant HRR genes: BRCA1, BRCA2, CHEK2, ATM, and CDK12. Results: HRR gene pathogenic or likely pathogenic alterations were identified in 18% (CI 95% = 16-20) of the patients, with BRCA2 being the most frequently altered gene (6%), followed by ATM (5%), CDK12 (4%), BRCA1 (2%), and CHEK2 (1%). Eleven percent had variants of uncertain significance. Only 13% of the samples were rejected due to poor DNA quality, low tumor content or sample age exceeding 5 years, and 2% of the samples analyzed failed since the minimum library technical quality score was not achieved. The average turnaround time for results was 18 ± 3 days. Conclusions: Centralized HRR testing in mCRPC patients in Spain was feasible, efficient and reliable, identifying pathogenic alterations in 18% of the cases, similarly to the prevalence described in the literature. This testing approach facilitates precision medicine by improving the detection of actionable HRR alterations.