Genetic testing patterns for homologous recombination repair (HRR) alterations in patients with metastatic prostate cancer (mPC): An assessment at the University of Rochester (UR).
322 Background: Germline and somatic HRR alterations are present in 12% and 20% of patients with mPC, respectively, and can have treatment implications. NCCN guidelines recommend offering genetic testing for patients with mPC. This study examines genetic testing patterns in patients with mPC at UR. Methods: We conducted a retrospective study of all patients (n = 240) with mPC who saw medical oncology at UR from 10/1/2017 to 4/1/2018. We abstracted the following data from medical records: patient demographics, mPC characteristics, types of genetic testing, and clinically significant (CS) HRR alterations as defined by Myriad, Ambry, and Foundation One. To compare characteristics of patients who had genetic testing to those who did not, we used non-parametric Wilcoxon rank-sum test for continuous variables and Fisher’s exact test for categorical variables. Results: The median age at mPC diagnosis was 71 years (range: 42-93 years), 86.3% were white, and 35% had mPC at initial diagnosis. 64 patients (26.7%) were offered genetic testing and 40 patients (16.7%) completed germline (n = 12), somatic (n = 21), or both germline and somatic genetic testing (n = 7). Median time from diagnosis of mPC to germline and somatic genetic testing were 9 months and 35 months, respectively. Among the 24 patients who were offered, but did not have testing, the reasons were: patients’ refusal (n = 10), death/hospice care (n = 7), insurance issue (n = 3), patient’s preference to have somatic testing at disease progression (n = 3), and missed genetic counseling visit (n = 1). Compared to patients who did not have genetic testing, those who had testing were younger at the time of mPC diagnosis (63.5 vs 73.0 years; p < 0.0001). CS HRR alterations were identified in 8 of 40 patients tested (20%): somatic HRR alterations include BRCA2 (n = 2), ATM (n = 1), CDK 12 (n = 1), and C HEK2 (n = 1); germline HRR alterations include BRCA2 (n = 2) and CHEK2 (n = 1). Conclusions: We report that approximately one-fourth of patients with mPC at UR had genetic testing offered, with a 20% prevalence of HRR alterations in those tested. Future research should develop strategies to address barriers to genetic testing.