Radiation Biology and Treatment Options in Radiation Oncology

It is a truly great honor for me to introduce Dr. H. Rodney Withers, the recipient of the Charles F. Kettering Prize on this, the 20th anniversary of the General Motors Cancer Research Foundation awards. Dr. Withers is receiving the Kettering Prize for his exceptional contributions to the field of modern radiotherapy. Dr. Withers received his medical degree from the University of Queensland Medical School in Brisbane, Australia in 1956, followed by a Ph.D. degree from the University of London where he worked with Dr. Gray. After spending two years as a visiting research scientist at the National Cancer Institute, working with Dr. Mortimer Elkind, he became an associate professor of radiotherapy at the University of Texas M.D. Anderson Cancer Center. In 1971, he became a professor of radiotherapy at M.D. Anderson, and then, in 1980, he moved to UCLA, where he became a professor in the Department of Radiation Oncology. After a two-year stint as professor and director of the Institute of Oncology at the Prince of Wales Hospital, University of New South Wales, Sydney, Australia from 1989 to 1991, Dr. Withers returned to UCLA where he is currently professor and chair of the Department of Radiation Oncology. Dr. Withers has received numerous honors in recognition of his scientific achievements, including the Polish Academy of Medicine Prize in 1989, a Gold Medal Distinguished Scientist award from the American Society of Therapeutic Radiology and Oncology in 1991, and the Fermi Award from the U.S. Department of Energy in 1997. Dr. Withers' scientific achievements are immense. His research has revolutionized basic concepts in radiation biology. This research has led to improved survival of cancer patients while sparing normal tissues from radiation damage. Dr. Withers' discoveries have led to the use of smaller than conventional incremental radiation doses, a concept called hyperfractionated radiation, in order to provide differential sparing of the late-reacting normal tissues as compared to the tumor tissue. By exploiting cell cycle related fluctuations in radiosensitivity, Dr. Withers formulated a treatment regimen which allowed the intensification of radiation exposure to decrease tumor cell repopulation while allowing repair of radiation damage in normal tissues. Dr. Withers beautifully applied the principles he derived from his animal models to clinical trials in human patients. Hyperfractionated radiation has now been shown in randomized clinical trials to provide improved disease-free survival in patients with head and neck cancer as compared to patients receiving standard fractionation radiotherapy. A second major discovery of Dr. Withers' is that certain tumors, especially squamous cell carcinomas, can respond to cytotoxic therapy with greatly accelerated growth, a concept called accelerated repopulation. Regrowth of tumor cells is a concern in the delivery of both chemotherapy and radiotherapy. Thus, long-term treatment interruption to allow recovery from toxicity may allow tumor cell repopulation to exceed tumor cell kill. Dr. Withers' research in this area has allowed treatment regimens to be designed to minimize this accelerated repopulation by tumor cells. In summary, Dr. Withers' research has provided the basis for modern radiation therapy concepts worldwide. I am very proud today to introduce such a distinguished scientist, and I look forward to Dr. Withers' talk titled Biology of Dose Fractionation in Radiation Oncology.