Whole-exome sequencing and clinical interpretation of formalin-fixed, paraffin-embedded tumor samples to guide precision cancer medicine

Whole-exome sequencing (WES) has emerged as a transformative technology for biological discovery, but technical difficulties have so far prevented its widespread clinical use. Here, Eliezer Van Allen and colleagues are able to perform production-scale WES on small amounts of clinically acquired formalin-fixed, paraffin-embedded tumor tissues. Using a newly created WES clinical interpretation algorithm, they apply the complete clinical WES framework prospectively to patients and demonstrate how it can be used to directly affect patient care. Translating whole-exome sequencing (WES) for prospective clinical use may have an impact on the care of patients with cancer; however, multiple innovations are necessary for clinical implementation. These include rapid and robust WES of DNA derived from formalin-fixed, paraffin-embedded tumor tissue, analytical output similar to data from frozen samples and clinical interpretation of WES data for prospective use. Here, we describe a prospective clinical WES platform for archival formalin-fixed, paraffin-embedded tumor samples. The platform employs computational methods for effective clinical analysis and interpretation of WES data. When applied retrospectively to 511 exomes, the interpretative framework revealed a 'long tail' of somatic alterations in clinically important genes. Prospective application of this approach identified clinically relevant alterations in 15 out of 16 patients. In one patient, previously undetected findings guided clinical trial enrollment, leading to an objective clinical response. Overall, this methodology may inform the widespread implementation of precision cancer medicine.