Radiation biology.

On a few occasions in the past, radiobiological experiments profoundly influenced the practice of radiotherapy. For example, it was shown in the 1920s that animals could be sterilized without damage to the skin of the scrotum if the testes were irradiated in multiple fractions, whereas in a single dose, sterilization was not possible without significant skin damage. These experiments led to the fractionation patterns used in conventional radiotherapy today. Few experiments have had such a dramatic impact, but since World War II, studies with mammalian cells in culture, transplantable animal tumors, and normal tissue systems produced an impressive body of experimental data. Conventional radiotherapy techniques now can be understood in terms of the basic principles of radiobiology. New horizons in radiotherapy are also suggested. These include the following: (1) altered fractionation schedules, including hyperfractionation and accelerated treatment; (2) the selection of groups of patients likely to benefit from neutrons; and (3) The use of hyperthermia alone or as an adjunct to radiation.