Germline genetic testing for inherited prostate cancer in practice: Implications for genetic testing, precision therapy, and cascade testing.

BACKGROUND: Genetic testing capability and guidelines are rapidly expanding to assess inherited prostate cancer (PCA). Clinical genetic data from multigene testing can provide insights into the germline pathogenic variant (PV) spectrum and correlates in men with PCA unselected for metastatic disease to optimize identification of men for genetic evaluation and management.
METHODS: A retrospective cross-sectional analysis was conducted of de-identified clinical genetic testing data from a large commercial genetic testing laboratory in the US. ICD-10 claims codes were used to identify men with PCA, along with family history data. Gleason score was abstracted from test request forms. Overall PV rate among men with PCA was estimated, along with PVs in DNA repair genes. Family history and Gleason score association to germline DNA repair PVs was assessed using Fisher's exact test with correction for false-discovery.
RESULTS: As of August 2017, genetic results were available on 1328 men with PCA. Overall PV rate was 15.6%, with 10.9% of PV in DNA repair genes. PVs were most commonly identified in BRCA2 (4.5%), CHEK2 (2.2%), ATM (1.8%), and BRCA1 (1.1%). Breast cancer family history was significantly associated with germline DNA repair PVs (OR 1.89, [95%CI 1.33, 2.68], P = 0.003). Among men with Gleason score>= 6 (n = 706), Gleason> = 8 was significantly associated with DNA repair PVs (OR 1.85 [95%CI 1.22, 2.80], P = 0.004).
CONCLUSIONS: A substantial proportion of men with PCA unselected for metastatic disease carry germline DNA repair PVs. Breast cancer family history and high Gleason score are important predictors to identify men with PCA who may carry germline DNA repair PVs. Our findings support current NCCN guidelines and have implications for genetic assessment, therapeutic management, and cascade testing for men with PCA and their families.