Ingestion of selenium and other antioxidants during prostate cancer radiotherapy: a good thing?

Radiation and many chemotherapy agents work to kill cells by inducing free radicals that damage DNA and proteins. Antioxidants such as vitamin E, beta carotene, lycopene, and selenium have been associated with a reduction in cancer risk when ingested by prostate cancer patients. Selenium is a promising agent currently being evaluated as a prostate cancer prevention agent. Selenium is an essential trace element and is involved in antioxidant protection and the redox-regulation in humans. Several adverse effects of radiotherapy and chemotherapy in cancer patients have been linked to oxidative cell processes in the human body. Selenium supplementation may protect healthy tissues and reduce the side effects of treatment. Despite two decades of research into this question, no clear answer has appeared. Therefore, understanding the mechanism(s) by which dietary nutrients exert their effects in prostate carcinogenesis, may lead to the exploitation of new chemoprevention agents. A large body of epidemiological evidence, including observational, trials, and randomized controlled clinical trials, support the proposition that selenium may prevent prostate cancer in humans. These clinical studies are supported by in vitro and in vivo data using prostate cancer models. This systematic review provides the first evidence that antioxidant supplementation during chemotherapy holds potential for reducing dose-limiting toxicities. The pre-clinical and clinical evidence as to whether ingestion of supplemental selenium, in addition to radiotherapy/chemotherapy is beneficial, detrimental or neutral towards patient outcome is also discussed.