Advances in brachytherapy.

Abstract

Soon after the discovery of radioactivity in 1896, small encapsulated sources of radioactive materials were implanted in tumors to treat malignancies. Clinical use of radioactive sources at short distances from or inside a tumor volume is termed brachytherapy, as opposed to teletherapy, which employs a source of radiation external to the patient at a large distance (about 1 m) from the tumor. Brachytherapy continues to play an important role in the management of cancers of several sites, including the uterine cervix, endometrium, and prostate. Compared with conventional external beam therapy, the physical advantages of brachytherapy result from a superior localization of dose to the tumor volume. In brachytherapy, as radiation is continuously delivered over a period of time, repair of sublethal and potentially lethal damage, proliferation, and other cell kinetic effects modify the radiation response of tumor and normal tissues, resulting in complex dose-rate effects that also influence the therapeutic ratio for brachytherapy.