LAUSR

1576Background: Sequencing more genes increases the chance of finding a pathogenic mutation and/or a variant of uncertain significance (VUS). Little is known about potential harms of multiplex testing for cancer risk, such as unwarranted surgery or adverse psychological effects. Methods: We conducted a prospective trial of sequencing 25 genes: APC, ATM, BARD1, BMPR1A, BRCA1, BRCA2, BRIP1, CDH1, CDK4, CDKN2A, CHEK2, EPCAM, MLH1, MSH2, MSH6, MUTYH, NBN, PALB2, PMS2, PTEN, RAD51C, RAD51D, SMAD4, STK11, TP53. Patients were eligible if they met standard testing guidelines or predictive models estimated ≥2.5% mutation probability. Participants were surveyed 3 months post-test: the Multidimensional Impact of Cancer Risk Assessment (MICRA) scale measured distress, uncertainty and positive experiences. We report on the fully accrued trial (N = 2000). Results: 1998/2000 (99.9%) participants currently have reported results: 12.1% tested positive for a pathogenic mutation (Pos), 34.5% had VUS only and 53.5% tested ne...