Simon Powell, MD, PhD

Rosen and colleagues have provided a comprehensive review of the biological basis of radiation sensitivity, including recent insights into the DNA damage response. They correctly emphasize that local control of tumors is still a major clinical problem, and that a better understanding of the biological basis for radiation resistance/sensitivity has significant potential to be exploited for therapeutic gain. They also assert that further progress in local tumor control is unlikely to be achieved by technologic improvements in the delivery of such radiation therapies as three-D (3D) conformal radiotherapy, intensity-modulated radiation therapy (IMRT), altered fractionation, or even chemosensitization.