Germline variants and family history in caucasian and African-American prostate cancer.

Abstract

e16548 Background: Family history (FH) is a well-documented risk factor for prostate cancer (PCa). Previously, germline pathogenic variants (PVs) have been identified in metastatic PCa. The goal of this study was to fully evaluate cancer FH and assess PVs detected in PCa patients undergoing both detailed FH ascertainment and germline genetic testing. Methods: FHs were collected from 535 PCa pts (Caucasian (Ca) n = 359, African American (AA) n = 85, Other n = 18) at Tulane from 2015-2016. Age at diagnosis, Gleasons, and the presence of metastases at any time were noted for these pts. Chi-square and the Mann-Whitney U tests were performed to identify relationships between clinical parameters and FH. 124 PCa pts including those with both localized and metastatic disease were identified with FHs that met guidelines for genetic testing. Genetic testing was done using a commercially available panel (Invitae, San Francisco, CA) of 25-79 cancer-related genes for mutations/selected exon deletions/duplications. Results: Of the 124 tested pts, 20 pts (16.1%) had ≥ 1 germline PV and 47 pts (37.9%) had ≥ 1 germline variant unknown significance. PVs included: BRCA2 (n = 4), BRCA1 (n = 3), CHEK2 (n = 3), MUTYH (n = 3), ATM (n = 2), TP53 (n = 1), MITF (n = 1), NBN (n = 1), PMS2 (n = 1), and RAD51D (n = 1). No PVs were detected in AA pts (n = 20). 435 of 535 PCa pts (81.3%) had a cancer FH with prostate (37.8%), breast (28.2%), lung (16.4%), colorectal (14.8%), and pancreatic (7.5%) cancer being most common. 281 pts (52.5%) had ≥ 2 relatives with cancer. Pts with PCa FH were more likely to be dx age ≤ 55 (p = 0.017). Median age was younger at dx for pts with PCa FH (p = 0.0005). PCa FH did not alter Gleason or metastatic rate. FH influenced age at dx for Ca men (p = 0.0009, 58 vs. 62.5 and Ca men with PCa FH) were 1.55x more likely to develop metastases (p = 0.035). In AA pts, there were no significant associations between FH, and metastases or age at dx. Conclusions: The most prevalent germline mutations in this cohort were in DNA repair pathway genes. Pts with PCa FH were younger at dx than those without PCa FH. Further studies are needed to understand the co-segregation of PCa with other cancers and genetic studies are needed to clarify the mechanisms of these trends which may differ between Ca and AA men.