Predicting response to clinical radiotherapy: past, present, and future directions.

BACKGROUND Personalized radiation therapy holds the promise that the diagnosis, prevention, and treatment of cancer will be based on individual assessment of risk. Although advances in personalized radiation therapy have been achieved, the biological parameters that define individual radiosensitivity remain unclear. METHODS This review focuses on discussing the field of radiosensitivity predictive assays, a technology central to the concept of personalized medicine in radiation oncology. Two novel approaches, DNA end-binding complexes and gene expression classifiers, show promise in solving some of the logistic problems associated with previous assays. RESULTS Current data suggest that predicting clinical response to radiotherapy is possible. The delivery of this promise depends on the ability to define the variables that define response to clinical radiotherapy. A successful predictive assay is key to the development of personalized treatment strategies in radiation oncology. CONCLUSIONS Novel technologies need to be developed that will improve our understanding of the biological variables that define clinical tumor response and will lead to the development of a clinically useful assay.