Use of Amifostine for Cytoprotection during Radiation Therapy: A Review.

BACKGROUND: Radiation therapy is a cornerstone of the therapeutic modalities used in modern oncology. However, it is sometimes limited in its ability to achieve optimal tumor control by radiation-induced normal tissue toxicity. In delivering radiation therapy, a balance must be achieved between maximizing the dose to the tumor and minimizing any injury to the normal tissues. Amifostine was the first Food and Drug Administration (FDA)-approved clinical radiation protector intended to reduce the impact of radiation on normal tissue, lessening its toxicity and potentially allowing for increased tumor dose/control. Despite being FDA-approved almost 20 years ago, Amifostine has yet to achieve widespread clinical use. SUMMARY: A thorough review of Amifostine's development, mechanism of action, and current clinical status were conducted. A brief history of Amifostine is given, from its development at Walter Reid Institute of Research to its approval for clinical use. The mechanism of action of Amifostine is explored. The results of a complete literature review of all prospective randomized trials to date involving the use of Amifostine in radiation therapy are presented. The results are arranged by treatment site and salient findings discussed. Side effects and complications to consider in using Amifostine are reviewed. Key Messages: Amifostine has been explored as a radiation protectant in most radiation treatment sites. Studies have demonstrated efficacy of Amifostine in all treatment sites reviewed, but results are heterogeneous. The heterogeneity of studies looking at Amifostine as a clinical radiation protectant has precluded a definitive answer on its efficacy. Complicating its clinical use is its toxicity and delivery requirements. Amifostine has largely fallen out of use with the advent of intensity modulated radiation therapy (IMRT). However, side effects with IMRT remain a challenge and concern. The use of Amifostine in the IMRT era has been poorly explored and is worthy of future study.