Detection rates of multigene panel and exome testing in patients with previous negative BRCA1/2 results

Since panel genetic testing has become widely available, national guidelines recommend that individuals who previously underwent BRCA1/2-only testing should undergo updated testing to include other hereditary breast and ovarian cancer predisposition genes. Our study assessed the yield of additional hereditary cancer predisposition testing in patients who previously underwent negative BRCA1/2 testing. Additionally, our study included a small pilot to evaluate whole exome sequencing in patients with a strong family history. Patients enrolled in a registry study who previously underwent negative BRCA1/2 testing were included and stratified into three categories based on personal and family cancer history-strongly suggestive, moderately suggestive, and possibly suggestive. Updated testing with a 36-gene pan-cancer panel was performed on most participants. A selected set of participants had whole exome sequencing. Patients with a pathogenic variant identified were offered clinical confirmatory testing. Rates of positive test results were compared among the three groups. Clinically relevant pathogenic variants in non-BRCA1/2 genes from the 36-gene panel test were identified in 8.1% of participants, most commonly in PALB2 (1.9%), ATM (1.2%), and MSH6 (1.2%). Positive findings were more common in patients with strongly suggestive history, but the differences were not statistically significant. Exome testing in individuals with a strongly suggestive personal and family history did not yield novel findings. Our findings aligned with previous studies and support the use of expanded gene panel testing in all patients meeting testing criteria who previously underwent negative BRCA1/2 testing. Our small pilot whole exome sequencing did not identify any novel finding.