Defining, Identifying, and Understanding “Exceptional Responders” in Oncology Using the Tools of Precision Medicine

Abstract Widely available molecular profiling technology, including next-generation sequencing has changed the landscape of drug development in cancer. An increasing number of clinical trials in early drug development require patient selection based on molecular alterations. Concurrently, efforts to identify molecular alterations in tumors that exhibited exceptional response after systemic treatment with standard or investigational agents have been published or are in progress. These discoveries may ultimately serve as predictive markers or “actionable mutations” for future therapies. To test the feasibility of collecting the archival tissues from proposed exceptional responder patients and successful subsequent molecular profiling, the National Cancer Institute opened a nationwide exceptional responder initiative protocol in 2014. In addition, an increasing number of exceptional responder cases have been identified and published from academia institutions. The Network of Enigmatic Exceptional Responders study uses crowdsourcing to identify exceptional responders and will molecularly profile tumors to discern molecular correlates with exceptional response. In this review, we discuss the potential role of exceptional responder molecular analysis in new biomarker discovery efforts to further advance precision medicine in oncology therapeutics.