Complexities of Next-Generation Sequencing in Solid Tumors: Case Studies

With the promise and potential of clinical next-generation sequencing for tumor and germline testing to impact treatment and outcomes of patients with cancer, there are also risks of oversimplification, misinterpretation, and missed opportunities. These issues risk limiting clinical benefit and, at worst, perpetuating false conclusions that could lead to inappropriate treatment selection, avoidable toxicity, and harm to patients. This report presents 5 case studies illustrating challenges and opportunities in clinical next-generation sequencing interpretation and clinical application in solid tumor oncologic care. First is a case that dissects the origin of an ATM mutation as originating from a hematopoietic clone rather than the tumor. Second is a case illustrating the potential for tumor sequencing to suggest germline variants associated with a hereditary cancer syndrome. Third are 2 cases showing the potential for variant reclassification of a germline variant of uncertain significance when considered alongside family history and tumor sequencing results. Finally, we describe a case illustrating challenges with using microsatellite instability for predicting tumor response to immune checkpoint inhibitors. The common theme of the case studies is the importance of examining clinical context alongside expert review and interpretation, which together highlight an expanding role for contextual examination and multidisciplinary expert review through molecular tumor boards.