Evaluation of a cancer gene sequencing panel in a hereditary risk assessment clinic.

Abstract

7 Background: Multiple-gene sequencing panels are entering clinical practice. We report on research testing with a custom sequencing panel comprising 43 genes and 32 cancer-associated variants among patients referred for assessment of hereditary breast and ovarian cancer risk. Methods: Patients referred to the Stanford Cancer Genetics Program for clinical BRCA1 and BRCA2 (BRCA1/2) mutation testing from 2002-2012 were invited to donate a blood sample for research on an Institutional Review Board-approved protocol. Blood samples were frozen at -80 degrees, and DNA extracted after <1-10 years. The entire coding region, exon-intron boundaries (+/- 10bp) and all known pathogenic variants in other regions were sequenced for 43 genes that have published associations with risk of breast, ovarian and other cancers. An additional 32 cancer-associated variants were also sequenced. Clinically significant results were disclosed to patients. Results: Germline DNA samples were sequenced from 199 women: 141 had breast cancer, and 57 carried known BRCA1/2 mutations. Analytic results for BRCA1/2 sequencing and pathogenicity interpretations were concordant with prior clinical testing for all patients. Twenty variants designated as pathogenic, either based on published literature or due to a novel truncating or splice donor/acceptor effect, were observed in genes other than BRCA1/2, including ATM, BLM, CDH1, CDKN2A, MUTYH, MLH1, NBN, PRSS1, and SLX4. Thirteen patients had pathogenic variants warranting a change in cancer screening or risk reduction based on practice guidelines; they were invited for confirmatory clinical testing and counseling. One 53-year old patient with a personal history of breast and endometrial cancers was found to carry a pathogenic MLH1 mutation; she underwent risk-reducing salpingo-oophorectomy and colonoscopy, with removal of a tubular adenoma. Conclusions: Among patients referred for BRCA1/2 mutation testing, a comprehensive sequencing assay identified 20 [10.1%, 95% confidence interval (CI) 6.5%-15.1%] pathogenic mutations in other genes, of which 13 (6.5%, CI 3.8%-11%) prompted a change in care. Disclosure of research results to participants was feasible and well-tolerated.