Biomarker Study of Neoadjuvant Vitamin E in Patients With Locally Treatable Prostate Cancer

- Prostate Cancer

Prostate cancer is the most common malignancy in American men. It was estimated that nearly 235,000 men in the United States would be diagnosed with prostate cancer and nearly 27,000 men would die. The treatment of localized prostate cancer includes surgery, radiation therapy, or watchful waiting. The relative benefits of these approaches is unclear and treatment choices are individualized and often patient driven. There is currently no proven benefit to receiving preoperative hormonal therapy for patients undergoing radical prostatectomy. As opposed to patients undergoing external beam radiation therapy, for patients undergoing brachytherapy pre treatment hormonal therapy is used in approximately 40% of patients. Thus, these patients offer a unique opportunity to test novel agents in the neoadjuvant setting.

- Vitamin E

The term vitamin E was introduced by Evans and Bishop to describe a dietary factor important for reproduction in rats. Natural vitamin E includes two groups of closely related fat-soluble compounds, the tocopherols and tocotrienols. Eight analogous compounds are widely distributed in nature. Rich, natural sources of vitamin E are edible plant oils. Distinct biological effects of different forms of vitamin E can be distinguished at a molecular level. Vitamin E is the major hydrophobic chain-breaking antioxidant that prevents the propagation of free radical reactions in the lipid components of membranes, vacuoles and plasma lipoproteins.

As an antioxidant, vitamin E acts in cell membranes where it prevents the propagation of free radical reactions. Non-radical oxidation products are formed by the reaction between alpha-tocopheryl radical and other free radicals, which are conjugated to glucuronic acid and excreted through the bile or urine. Vitamin E is transported in plasma lipoproteins.

Most studies of the safety of vitamin E supplementation have lasted for several months or less, so there is little evidence for the long-term safety of vitamin E supplementation. The Food and Nutrition Board of the Institute of Medicine has set an upper tolerable intake level (UL) for vitamin E at 1,000 mg (1,500 IU) for any form of supplementary alpha-tocopherol per day. Based for the most part on the result of animal studies, the Food and Nutrition Board decided that because vitamin E can act as an anticoagulant and may increase the risk of bleeding problems this is the highest dose unlikely to result in bleeding problems (http://dietary-supplements.info.nih.gov/factsheets/vitamin.asp).

The dose of vitamin E used in the Selenium and vitamin E prostate cancer prevention trial (the SELECT trial) was 400 IU per day and thus this is the dose chosen for this study.