The role of amifostine as a radioprotector.

Effective radiotherapy for patients with cancer should include maximal tumor cell killing with minimal injury to normal tissue. Radiation doses that can be delivered, without causing severe damage to surrounding normal tissues, can be insufficient to eradicate a tumor. Agents have been developed to protect normal tissue from the toxicities of radiation. The aminothiol amifostine (Ethyol) is the subject of extensive research as a protector. Several studies have demonstrated that amifostine protects normal tissues from both acute and late radiation damage without protecting the tumor. This article reviews the physicochemical basis of radiation therapy on biologic tissues and the mechanisms responsible for the protective effects of amifostine. The increasing body of biochemical, preclinical, and clinical data can justify the use of protectors such as amifostine with radiotherapy to provide improved therapeutic efficacy and quality of life for the patient. This article will review the current understanding of the nature of toxicity resulting from radiation therapy and the benefits that can be derived from using protection to increase the tolerance of normal tissue to radiation damage.