Performance of mutation risk prediction models in a racially diverse multi-gene panel testing cohort.

Abstract

1523 Background: Mutation carrier prediction models are clinically useful tools for identifying candidates for genetic counseling and testing. Consensus guidelines recommend germline genetic testing for those with a carrier probability (CP) of approximately 5% or higher. However, prediction models may perform less well among racial/ethnic minorities. Our hypothesis is that pathogenic mutations (PM) are identifiable in a clinically meaningful fraction of racially/ethnically diverse patients with a CP of < 5%. Methods: We conducted a multicenter prospective clinical trial of patients undergoing cancer-risk assessment using a 25 gene panel, which include 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 recruited from August 2014 to November 2016 at three centers. Patients were enrolled if they met standard clinical criteria for genetic testing or were predicted to have a ≥2.5% probability of inherited cancer susceptibility using validated prediction models. We evaluated the CP of patients with a PM in BRCA1, BRCA2, and/or a mismatch repair (MMR) gene using the following models: (1) BRCApro, (2) MMRpro and (3) PREMM1,2,6. Results: Of 2000 patients enrolled in this cohort, 80.6% are female (n = 1612). Regarding race/ethnicity, the cohort is 40.1% Non-Hispanic White (n = 802), 37.4% Hispanic (n = 748), 11.5% Asian (n = 230), 3.9% Black (n = 78), and 7.1% Other (n = 142). Among 241 (12.1%) patients who tested positive for a pathogenic mutation, 76 (31.5%) patients had a BRCA1 or BRCA2 mutation. Of those, 52 (68.4%) patients had a BRCApro CP of < 5%. Thirty-eight (15.8%) patients had a pathogenic mutation in an MMR gene: 19 (50.0%) had an MMRpro CP of < 5%, while 13 (34.2%) had a PREMM1,2,6 CP of < 5%. The racial/ethnic distribution of BRCA1/2 or MMR mutation carriers is similar to that of the whole cohort. Conclusions: In a diverse cohort of patients undergoing 25-gene multiple-gene panel testing, half or more carriers of BRCA1/2 or MMR mutations had a CP of < 5%, the consensus guideline-recommended cutoff for genetic testing. These results support a lower threshold for genetic testing guidelines. Clinical trial information: NCT02324062.