THE BETA-CAROTENE AND RETINOL EFFICACY TRIAL (CARET) FOR CHEMOPREVENTION OF LUNG-CANCER IN HIGH-RISK POPULATIONS - SMOKERS AND ASBESTOS-EXPOSED WORKERS

CARET is a multicenter, two-armed, double-masked randomized chemopreve ntion trial in Seattle, Portland, San Francisco, Baltimore, Connecticu t, and Irvine, to test whether oral administration of beta-carotene (3 0 mg/day) plus retinyl palmitate (25,000 IU/day) can decrease the inci dence of lung cancer in high risk populations, namely, heavy smokers a nd asbestos-exposed workers. The intervention combines the antioxidant action of beta-carotene and the tumor suppressor mechanism of vitamin A. As of April 30, 1993, CARET had randomized 1,845 participants in t he 1985-1988 pilot phase plus 13,260 ''efficacy'' participants since 1 989; of these, 4,000 are asbestos-exposed males and 11,105 are smokers and former smokers (44% female). Accrual is complete everywhere excep t Irvine, which was the last center added (1991), and the safety profi le of the regimen to date has been excellent. With 14,420 smokers, 4,0 10 asbestos-exposed participants, and 114,100 person-years through Feb ruary 1998, we expect CARET to be capable of detecting a 23% reduction in lung cancer incidence in the two populations combined and 27,49,32 , and 35% reductions in the smokers, female smokers, male smokers, and asbestos-exposed subgroups, respectively. CARET is highly complementa ry to the alpha-tocopherol-beta-carotene study in Finland and the Harv ard Physicians Health Study (beta-carotene alone) in the National Canc er Institute portfolio of major cancer chemoprevention trials.