This chemoprevention trial tests the efficacy of retinol and beta- carotene in preventing lung cancer in two related high-risk populations: (a) heavy smokers recruited from insurance-based sources, and (b) current and former workers with heavy occupational asbestos exposure recruited from workers' compensation and employment-based sources. The double-blind, two-arm, randomized trial compares placebos with a daily combination of 30 mg beta- carotene plus 25,000 IU retinol. Successful recruitment, excellent compliance, and minimal side effects have been shown thus far in over 1700 subjects enrolled in our two current chemoprevention projects using these agents. We propose to integrate the two high- risk populations in a cost-effective, multi-clinic strategy for this efficacy trial, with Seattle coordinating center for project management and data analysis. During the first three years of the new grant period (1988-91) we will evaluate accrual, coordination, and costs in five geographically-dispersed clinic sites to generate best estimates of the remaining needs for the full-scale enrollment and follow-up. Current assumptions and projections indicate that the full-scale study will be capable of detecting significant reductions in lung cancer incidence in the high-risk groups combined, and in either subgroup alone, with 13,000 smokers and 4000 asbestos-exposed subjects.
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