Lung cancer chemoprevention: a randomized, double-blind trial in Linxian, China.

We examined the effect of supplementation with four different combinations of vitamins and minerals in the prevention of lung cancer mortality among 29,584 healthy adults from Linxian, China. In accord with a partial factorial design, the participants were randomly assigned to take either a vitamin/mineral combination or a placebo for 5.25 years. The combinations tested in this trial were as follows: factor A, retinol and zinc; factor B, riboflavin and niacin; factor C, ascorbic acid and molybdenum; factor D, beta-carotene, alpha-tocopherol, and selenium. Lung cancer deaths (n = 147) identified during the trial period (1986-1991) and 10 years after the trial ended (1991-2001) were the study outcome. No significant differences in lung cancer death rates were found for any of the four combinations of supplements tested in this study, using log-rank tests (all P values are >0.20) or Cox proportional hazards models adjusted for age, sex, commune, and other treatments. No significant interactions were seen for age, sex, or smoking status. Supplementation with combinations of vitamins and minerals at nutrient-repletion levels for 5.25 years did not reduce lung cancer mortality in this nutrient-inadequate population in Linxian, China.