Tumor radiosensitivity and apoptosis.

With approximately 50% of all cancer patients receiving radiation therapy at some point in their treatment, increasing the sensitivity of tumor cells to the lethal effects of irradiation has the potential to significantly improve the rate of recovery from many malignancies. The major biological determinant of radiotherapy failure is tumor radioresistance. It is well known that tumors from the same histological group and stage of development are extremely heterogeneous in their sensitivity to radiotherapy. There are many factors which could affect tumor radiosensitivity. One cellular mechanism common to various therapeutic regiments, including radiation, is killing tumor cells via apoptosis. However, this killing is not always efficient. In this review the link between tumor sensitivity to radiation treatment and the capacity of tumor cells to be killed by apoptotic mechanisms will be discussed. Copyright 1999 Academic Press.