[1] Fred Hutchinson Canc Res Ctr, Div Clin Res, Seattle, WA 98104 USA
[2] Fred Hutchinson Canc Res Ctr, Div Publ Hlth Sci, Seattle, WA 98104 USA
[3] Univ Washington, Sch Med, Div Gastroenterol, Seattle, WA USA
[4] Fred Hutchinson Canc Res Ctr, Div Human Biol, Seattle, WA 98104 USA