γ-Tocopherol: a New Player in Prostate Cancer Prevention?

Extract

In this issue of the Journal, Helzlsouer et al. (1) report findings from a nested case–control study that examines plasma levels of α-tocopherol, γ-tocopherol, and selenium in relation to incident prostate cancer. The study suggests protective associations for α-tocopherol and selenium, although these were not statistically significant, as well as a strong protective association with γ-tocopherol. In a previous randomized intervention study designed to examine selenium supplementation in relation to recurrent skin cancer (2), a striking 65% reduction in prostate cancer risk was observed among men randomly assigned to receive selenium. In a subsequent nested case–control study (3) of 181 cases of advanced prostate cancer and 181 age-matched control pairs based on toenail selenium in the Health Professionals Follow-up Study, men in the highest quintile of selenium also had a 65% lower risk relative to those in the lowest quintile. A recent study by Nomura et al. (4) also suggests a benefit of selenium. Although the evidence for selenium as protective against prostate cancer appears to be quite promising, not all of the data are supportive. Finland began fortification of agricultural fertilizers with selenium in the fall of 1984. Although the average selenium intake subsequently increased twofold to threefold (5,6), national prostate cancer incidence and mortality rates did not appear to decrease appreciably, at least during the first decade. Perhaps a longer time period is required, although the randomized trial (2) demonstrated a reduction within several years.