Rates of germline genetic testing and DNA damage response mutations found through population-based recruitment of men with incident metastatic prostate cancer.
Authors: Khan Hiba , Wong Risa Liang , Darst Burcu , Pritchard Colin C. , Nelson Peter , Stanford Janet L. , Lin Daniel W. , Cheng Heather H. 
Published: June 2022

10501 Background: Approximately 10% of men with metastatic prostate cancer (mPC) have germline DNA damage response gene mutations (gDDRm), indicating candidacy for precision treatment. Consequently, national guidelines recommend germline genetic testing be offered to all men with mPC. It is currently unclear what the rates of testing are in the community, and barriers to testing are not well understood. We conducted a population-based study to better understand current rates of germline genetic testing in men with newly diagnosed mPC, and to determine whether removing major barriers of cost and access could expand uptake of germline genetic testing. Methods: This is a prospective observational study that identifies men ages 35-79y with mPC residing in a 13-county area of Washington State through the Surveillance, Epidemiology, and End Results (SEER) program (NCT04254133). Men with new diagnoses of mPC are contacted by mailed invitation and follow-up phone inquiry. Interested men are then invited to provide informed consent and complete a questionnaire about personal and family health history. A saliva collection kit for a 30-gene targeted panel of cancer predisposition genes (Color Genomics) is mailed to participants’ homes free of charge. Results are issued by phone and/or email with genetic counseling support, including discussion about cascade genetic testing if relevant. Results: As of Feb 9, 2022, 484 men with incident mPC diagnosed 1/2018-6/2021 were identified through SEER. 430 men were reached via a letter to their home address sent > 3 months after diagnosis. 175 of 430 (40.6%) men expressed interest and completed the questionnaire, the majority preferring to complete testing through mail after a phone-initiated introduction to the study. 164 of 175 men completed the consent process and were eligible. Of these 164 men, 45 (27.4%) reported prior genetic testing, and reports were requested and reviewed to ensure adequate testing. Ultimately, 121 of 164 (73.8%) participants initiated and 101/121 (83.5%) have completed genetic testing through the study. Nine percent (9/101) of participants completing testing as part of the study were found to have gDDRm. Conclusions: We used a population-based approach to understand the proportion of men with mPC undergoing germline genetic testing through clinical care, and the subsequent uptake of genetic testing when access and cost barriers are removed. The uptake of guideline-based germline genetic testing among men with mPC in the community prior to study enrollment is only 27.4%. With study interventions in the form of free testing through mail, and phone-based support, 83.5% of men in this community successfully completed testing. Further work in this study will aim to elucidate and attempt to eliminate other barriers in germline genetic testing to further improve testing rates in this community.