The negative results of the SELECT study do not necessarily discredit the selenium-cancer prevention hypothesis.
The lack of treatment options for the worried well prostate cancer patients and the issues of cancer recurrence and hormone resistant disease in cancer survivors remain enormous obstacles (1). However, the long latency of prostate cancer presents an ample opportunity to intervene before the disease can progress to an invasive state. Thus, there is a strong need for mechanismbased naturally occurring or synthetic agents that can inhibit prostate cancer development and/or progression and for agents that can improve cancer survivorship. Though the etiology of prostate cancer remains poorly understood, epidemiologic studies revealed a number of potential risk factors for prostate cancer. Risk factors that cannot be modified include age, race, and family history (2). However, risk factors that can be modified include lifestyle in general and specifically nutritional, environmental, and hormonal factors (2). Thus diet derived compounds have the potential to be safe and several agents have been shown to have chemopreventive potential against experimental prostate cancer, including retinoids, cartenoids (e.g., lycopene), vitamin E, indole-3-carbinol, isoflavone, polyphenols, and selenium (3). Researchers in the area of selenium-cancer prevention often receive questions from the general public, reporters from the media, and in some instances, clinicians about the form and dose of selenium people may take as supplement and what is the active form of selenium in our daily diet. At present, our knowledge on the mechanisms that may account for cancer prevention by various forms of selenium is poorly understood and is based primarily on animal model studies and assays conducted in cultured prostate cancer cells (4–6). Unfortunately, how such knowledge can be applied to humans is unclear and this void presents a great challenge in the design of future clinical trials. This commentary is not meant to provide a comprehensive review on the role of different forms and doses of selenium in