A RANDOMIZED CONTROLLED TRIAL FOR CHEMOPREVENTION OF GASTRIC-CANCER IN HIGH-RISK JAPANESE POPULATION - STUDY DESIGN, FEASIBILITY AND PROTOCOL MODIFICATION

We have initiated a population-based, double-blind, randomized control led trial to examine the effects of supplementation of beta-carotene a nd vitamin C on the incidence of gastric cancer. The subjects were par ticipants in an annual health screening program conducted by four muni cipalities in Akita prefecture, one of the regions with the highest mo rtality from gastric cancer in Japan. We measured their serum levels o f pepsinogens (PGs) I and II, and asked persons diagnosed with chronic atrophic gastritis (defined as PG I < 70 ng/ml and PG I/PG II ratio < 3.0) to take diet supplements containing 0 or 15 mg/day beta-carotene and 50 or 500 mg/day vitamin C for 5 years. During the first year of recruitment conducted in one village from June through September, 1995 , 52% (635/1214) of screening participants had chronic atrophic gastri tis and 73% (439/602) of eligible persons responded. However, in respo nse to a National Cancer Institute press report released on January 18 , 1996, indicating that two beta-carotene trials had shown no benefit and potential harm from the supplement, we discontinued the beta-carot ene and continued with the trial using only vitamin C. Of 397 particip ants remaining at this point, 77% (305) consented to stay in the study . The results indicate that a randomized controlled trial for cancer p revention is feasible in the Japanese asymptomatic population.