1. From the Fred Hutchinson Cancer Research Center, Seattle, WA (KFA, PDL, DM, EW, JDP, and JWL); the University of Washington (KFA, PDL, DM, SSE, EW, JDP, and JWL), Seattle, WA; the Center for Health Studies, Group Health Cooperative, Seattle, WA (KMN); and the Gastroenterology, Group Health Cooperative, Seattle, WA (JTY and AF)