Prostate Cancer Health Center

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Chemoprevention with selenium and vitamin E

The effects of selenium and vitamin E, alone or in combination, on the risk of prostate cancer were studied in the Selenium and Vitamin E Cancer Prevention Trial (SELECT [NCT00006392]).[22,23,24] SELECT was a randomized, placebo-controlled trial of selenium (200 �g/d from L-selenomethionine), vitamin E (400 IU/d of all rac-[alpha]-tocopheryl acetate), or both (planned follow-up for a minimum of 7 years and a maximum of 12 years) for prostate cancer prevention. The primary endpoint was prostate cancer incidence as determined by routine clinical management.

Neither 200 �g of L-selenomethionine nor 400 IU of synthetic DL-(alpha)-tocopherol given orally, alone or combined, for a median of 5.5 years had significant effects on the primary or secondary endpoints. A statistically nonsignificant increased incidence of prostate cancer was observed in the vitamin E group (473 cases; hazard ratio = 1.13; 99% CI = 0.95-1.35; P = .06) compared with the placebo group (416 cases).[22]

Chemoprevention with lycopene

Evidence exists that a diet with a high intake of fruits and vegetables is associated with a lower risk of cancer. Which, if any, micronutrients may account for this reduction is unknown. One group of nutrients often postulated as having chemoprevention properties is the carotenoids. Lycopene is the predominant circulating carotenoid in Americans and has a number of potential activities, including an antioxidant effect.[25] It is encountered in a number of vegetables, most notably tomatoes, and is best absorbed if these products are cooked and in the presence of dietary fats or oils.

The earliest studies of the association of lycopene and prostate cancer risk were generally negative before 1995 with only one study of 180 case-control patients showing a reduced risk.[26,27,28,29] In 1995, an analysis of the Physicians' Health Study found a one-third reduction in prostate cancer risk in the group of men with the highest consumption of tomato products when compared with the group with the lowest level of consumption, which was attributed to the lycopene content of these vegetables.[30] This large analysis prompted several subsequent studies, the results of which were mixed.[31,32] A review of the published data concluded that the evidence is weak that lycopene is associated with a reduced risk because previous studies were not controlled for total vegetable intake (i.e., separating the effect of tomatoes from vegetables), dietary intake instruments are poorly able to quantify lycopene intake, and other potential biases.[33] Specific dietary supplementation with lycopene remains to be demonstrated to reduce prostate cancer risk.

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