Recent developments in radiotherapy.

Radiation oncology is a dynamic discipline. The radiobiologic basis for understanding and anticipating treatment effects continues to grow. Improved understanding is permitting study of altered fractionation regimens and safer integration into the clinic of high-dose-rate brachytherapy. A new agent, SR 4233, may completely revise clinical approaches to tumor hypoxia, especially intermittent (or "dynamic") hypoxia. The availability of computer technology that permits three-dimensional treatment planning with unusual beam and treatment table orientations should result in isodose lines that conform very tightly to desired treatment volumes, permitting higher doses of treatment with acceptable normal-tissue risk. The biology of cytotoxic drug and irradiation interactions and of cytokine and irradiation interactions is an area of growing promise. Combined chemotherapy and radiotherapy treatments have, in the past year, suggested major improvements in the management of esophageal and laryngeal cancer. The importance of local and regional tumor control in contributing to clinical disease course is being understood with increasing clarity, validating the development of technically demanding new approaches to administering irradiation and the use of adjunctive radiotherapy following chemotherapy for selected neoplastic diseases.