Clinical Utility of Genomic Sequencing for Hereditary Cancer Syndromes: An Observational Cohort Study

PURPOSE: Genomic sequencing (GS) is increasingly used to improve diagnoses and inform targeted therapies. GS can also be used to identify the 10% of cancer patients with an underlying hereditary cancer syndrome (HCS), who can benefit from surveillance and preventive surgery that reduce morbidity/mortality. However, the evidence on clinical utility of GS for HCS is limited: we aimed to fill this gap by assessing yield of all cancer results and associated recommendations for patients undergoing GS for HCS. MATERIALS AND METHODS: An observational chart review and survey were conducted for cancer patients with previous uninformative cancer gene panel results, who received GS as part of the Incidental Genomics Trial (ClinicalTrials.gov identifier: NCT03597165). Descriptive statistics were used to describe demographics and clinical history. Proportions were calculated to compare frequencies of result types and recommendations made and followed. RESULTS: A total of 276 patients were eligible and included. Participants were mostly female (n = 240), European (n = 158), and with breast cancer history (n = 168). Yield: 25 patients (9.1%) received ≥1 pathogenic/likely pathogenic variant, 246 (89%) received ≥1 variant of uncertain significance (VUS), and 27 (10%) were negative. Most pathogenic variants (20/26) were in low/moderate cancer risk genes. The mean number of VUS was 2.7/patient and higher in non-Europeans versus Europeans (3.5 v 2.5, P < .05). Recommendations: Pathogenic variants triggered 100 recommendations in 21/25 patients; most were for genetic counseling, communication to relatives, and cascade testing. CONCLUSION: GS provided a modest increase in utility after first-tier cancer gene panels, at the cost of a high frequency of uncertain results. Furthermore, most positives were low/moderate cancer risk results that did not have corresponding evidence-based, management guidelines.