Challenges of diagnosing homologous recombination deficiencies in metastatic prostate cancer: a six-year experience from a single institution.

ABSTRACT

PURPOSE: We evaluated the prevalence of homologous recombination deficiencies (HRD) to determine the efficacy of different techniques and clinical characteristics of patients. METHODS: This retrospective study included patients with metastatic prostate cancer who underwent molecular testing at our hospital between 2016 and 2022. We used tumor tissue, ctDNA, and lymphocytes for somatic or germline testing. We analyzed the clinical characteristics and survival outcomes. RESULTS: 144 patients were tested (113 somatic, 21 germline, and 10 both). Technical issues prevented the analysis of 23 prostatic samples (18.7%). 12 (8.3%) patients had HRD. BRCA2 was the most frequent mutation (66.7%). Patients with HRD were younger (57.5 years). Patients with BRCA mutations had poorer survival (31.9 vs 56.3 months, p = 0.048). CONCLUSION: In our institution, 8.3% of the patients had HRD. Tumor tissue analysis failed in 18.7% of tests. ctDNA analysis is an alternative detection method. BRCA mutations are correlated with poor prognosis.