Skin Cancer Prevention Study (Greenberg et al., 1990)

U.S.^c

Secondary prevention; randomized, double-blind, placebo-controlled intervention

1,805 men and women with recent nonmelanoma skin cancer; aged 40–89 y

Linxian Cancer Prevention Study (Blot et al., 1993)

China

Primary prevention; randomized, double-blind, placebo-controlled intervention

29,584 poorly nourished men and women, aged 40–69 y

α-Tocopherol, β-Carotene Cancer Prevention Study (ATBC Cancer Prevention Group, 1994)

Finland

Primary prevention; randomized, double-blind, placebo-controlled intervention

29,133 male cigarette smokers, aged 50–69 y

Polyp Prevention Study (Greenberg et al., 1994)

U.S.

Secondary prevention; randomized, double-blind, placebo-controlled intervention

864 men and women with recent nonmelanoma skin cancer

The β-Carotene and Retinol Efficacy Trial (Omenn et al., 1996)

U.S.

Primary prevention; randomized, double-blind, placebo-controlled intervention

14,254 heavy smokers and 4,060 asbestos workers, aged 45–69 y

Cambridge Heart Antioxidant Study (Stephens et al., 1996)

U.K.^e

Secondary prevention; randomized, double-blind, placebo-controlled intervention

2,002 patients with coronary atherosclerosis, mean age 62 y