Diagnostic yield of multigene panel testing in an Israeli cohort: enrichment of low-penetrance variants.

BACKGROUND: Carriers of pathogenic variants (PVs) in moderate-high-penetrance cancer susceptibility genes are offered tailored surveillance schemes for early cancer diagnosis. The clinical implications of low-penetrance variant carriers are less clear. METHODS: Clinical and demographic data were retrieved for a cohort of Israeli individuals who underwent oncogenetic testing by the 30-gene cancer panel at Color Genomics laboratory, between 04/2013 and 12/2018. RESULTS: Of 758 genotyped individuals, 504 had been diagnosed with cancer prior to testing: 283 (56%) had breast cancer and 106 (21%) colorectal cancer. Pathogenic or likely pathogenic (P/LP) variants were detected in 123 (16%) individuals. Overall, 44 different P/LP variants were detected in 18/30 cancer susceptibility genes; 20 of them were founder/recurrent mutations. Of the carriers, 39 (32%), 10 (8%), and 74 (60%) carried high-, moderate-, or low-penetrance variants, respectively. After excluding low-penetrance variants, 7% (33/504) of all cancer patients, 6% of breast or ovarian cancer patients were found to be carriers, as well as 7% (14/203) of individuals with colonic polyps, and 4% (11/254) of cancer-free individuals. CONCLUSIONS: The diagnostic yield of moderate- and high-penetrance PVs using multigene panel testing was 6%, with 3.7% carriers of non-recurrent PVs. This yield should be discussed during pre-test counseling, and emphasizes the need for harmonized recommendations regarding clinical implications of low-penetrance variants.

Recurring pathogenic variants in the BRCA2 gene in the Ethiopian Jewish population. Founder mutations?

Mutations in the BRCA1 and BRCA2 genes increase the risk for various cancers including breast, ovarian, prostate, pancreas and melanoma. Identifying BRCA1/2 mutation carriers enables risk assessment, surveillance, early detection and risk reduction. In certain Israeli sub-populations recurring and founder mutations have been identified and for these, testing for founder mutations is simple, efficient and cost-effective. Founder mutations in the Jewish Ethiopian population have not been described. We report here the identification of a recurring BRCA2 mutation in the Ethiopian Jewish population; c.5159C>A; p.Ser1720Ter, which has only been described once before in this population. In addition, in another family of the same origin we found the BRCA2 c.7579delG; p.Val2527Ter mutation that has been previously described in two different Jewish Ethiopian families. In Israel genetic testing is performed in a sequential stepwise manner, first testing a panel of predominant mutations and if negative further testing by gene sequencing is offered. Recently it has been decided to expand the founder mutation panel to include mutations which have been found in two or more separate families. This new panel will include the BRCA2 c.7579delG; p.Val2527Ter mutation, and we recommend that the BRCA2 c.5159C>A; p.Ser1720Ter mutation should also be added to the new predominant mutation panel.