LAUSR

10593 Background: We sought to evaluate the feasibility of a Cascade Testing (CT) protocol for family members of probands with actionable germline mutations associated with endometrial or ovarian cancer. Here, we characterize proband compliance with contacting family members for CT and proband satisfaction/regret. Methods: In this prospective study, consenting patients with pathogenic germline mutations associated ovarian or endometrial cancer completed a demographic survey and were asked to contact first- and second-degree relatives with genetic testing results. After a 1–3-month period, probands completed a survey indicating how many relatives had been contacted. At 3 months following consent, probands were asked to complete the validated Impact of Event Scale (IES) and Decision Regret Scales (DRS). Characteristics of probands who contacted relatives and those who did not were compared. Results: The study has accrued 57 probands since opening in March 2019. Germline mutations identified in the 57 probands include 27 BRCA1 (47.4%); 21 BRCA2 (36.8%); 3 BRIP1 (5.3%); 2 MLH1 (3.5%); 2 MSH2 (3.5%); 3 MSH6 (5.3%); 3 PMS2 (5.3%); 1 EPCAM (1.8%); 1 RAD50 (1.8%). Twenty-four (42.1%) probands had a history of cancer (breast 12; ovarian 8; uterine 2; other 5). Of the probands, 32 (56.1%) completed follow-up questionnaires and 29 (50.9%) had contacted relatives about participating in CT. In total, 67 relatives were contacted. Probands contacted an average of 1 relative, ranging from 1-20. Of the 29 probands who contacted relatives, 13 (44.8%) completed IES and DRS questionnaires. The median IES score was 0 out of 75 (IQR 0.0-4.5) and the median DRS score was 0 out of 100 (IQR 0.0-11.3). When comparing characteristics of probands who contacted relatives with those who did not, those with annual household incomes <$75,000 were more likely to contact relatives vs those with incomes ≥$75,000 (77.8% vs 39.5%; p=0.01). There was no association between contacting relatives and personal cancer history, race/ethnicity, education status, or age (Table). Conclusions: Half of probands enrolled in this study contacted relatives about CT, and those with household incomes <$75,000 were more likely to contact relatives than those with higher incomes. Overall, probands reported little/no regret or distress after contacting relatives about genetic testing results.[Table: see text]