For prostate cancer, there are conflicting results. A meta-analysis based on serum alpha-tocopherol content reported an inverse correlation, with the difference between lowest and highest a 21% reduction in relative risk. In contrast, a meta-analysis of observational studies reported no relationship for dietary vitamin E intake. There were also conflicting results from large RCTs. The ATBC trial administered placebo or 50 mg/day alpha-tocopherol to male tobacco smokers for 5 to 8 years and reported a 32% decrease in the incidence of prostate cancer. Conversely, the SELECT trial of selenium and vitamin E for prostate cancer enrolled men ages 55 or older, mostly non-smokers, to consume a placebo or a 400 IU/day dietary supplement. It reported relative risk as a statistically significant 17% higher for the vitamin group.