Targeted Prostate Cancer Chemoprevention Trial With Tocotrienols

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Over the last two decades, an enormous amount of scientic effort has been devoted to studying the relationship between vitamin E and prostate cancer. This effort is well justied, since prostate cancer remains the most common cancer in American men after skin cancer and is the second leading cause of cancer deaths: over 220,000 men will develop prostate each year (U.S. Cancer Statistics Working Group 2011). Nevertheless, large-scale, well-designed clinical intervention studies have not shown that alpha-tocopherol prevents prostate cancer or cancer in general (Lippman et al. 2009; Ju et al. 2010; Wada 2012). Alpha-tocopherol is the primary form of vitamin E in the plasma of fasting subjects and the primary form of vitamin E in most vitamin supplements. Gamma-tocopherol is, however, the primary dietary form of vitamin E. Vitamin E is a term that refers to at least eight different compounds that fall into two general categories: tocopherols and tocotrienols. Tocotrienols are normally not present in human plasma at detectable levels, yet the evidence for their role in preventing prostate cancer is both extensive and compelling (Conte et al. 2004; Srivastava and Gupta 2006; McAnally et al. 2007; Barve et al. 2009; Campbell et al. 2011; Luk et al. 2011). Excellent reviews are available on the general anticancer effects of tocotrienols (Wada 2009, 2012; Ju et al. 2010). It is unlikely that an anticancer effect could be achieved by consuming a tocotrienol rich diet, and instead a supplement-possibly in the form of a soft gel-would be necessary. Despite the ever-increasing data supporting the antiprostate cancer role of tocotrienols, a well-designed chemoprevention trial has yet to be conducted. Given the negative results with alpha-tocopherol chemoprevention trials, a future prostate cancer chemoprevention trial with another isoform of vitamin E must be well justied and designed. Moreover, the cost effectiveness of any future tocotrienol chemoprevention trial must be given high priority.