Evaluation of a mainstream model of genetic testing for men with prostate cancer

1521 Background: In order to identify the ∼12% with inherited cancer predisposition, it is recommended that all men with metastatic prostate cancer (mPC) be offered testing. This has implications for treatment choices and cancer prevention in family. Limited geneticists/genetic counsellors globally present a major barrier to testing. We tested a potential solution, mainstreaming, where testing is performed by the patient’s oncologist. Methods: Men with mPC at three Australian sites were offered germline genetic testing at their medical oncology appointment. Panel testing ( ATM, BRCA1, BRCA2, BRIP1, CHEK2, EPCAM, FANCA, HOXB13, MLH1, MSH2, MSH6, NBN, PALB2, PMS2, RAD51D and TP53) was performed on saliva/blood (Invitae). Primary outcomes were clinician and patient acceptability (modified Royal Marsden Satisfaction Questionnaires). Secondary outcomes included mutation rates and cost-effectiveness. A sample size of 44 provided 90% power, with a one-sided alpha of 5%, to distinguish a proportion of men happy with mainstreaming of 80% vs. 60% or less. Allowing for 25% drop-out, we aimed to recruit 60 men. Results: Of 66 men offered testing from April to November 2019, 63 (95%) accepted. Four pathogenic variants were identified (2 BRCA2, 1 NBN, 1 MSH6). 48 patients and eight clinicians completed questionnaires. Acceptability was high. All (48/48) patients were happy to have been tested, and 45/48 (94%) were happy to have been tested at their oncology appointment. All were happy to receive their results from their oncologist. All clinicians were satisfied mainstreaming and 88% (7/8) felt confident doing so. Mainstreaming was cost-effective, requiring 87% fewer genetic consultations than traditional genetic counselling. Conclusions: This study shows that mainstreaming of men with mPC is feasible, resource efficient and acceptable to both clinicians and patients. Widespread implementation as a new standard of care would facilitate timely access to genetic testing for men with mPC.