[1] Univ Calif San Francisco, Dept Family & Community Med, Sch Med, San Francisco, CA 94143 USA
[2] Univ Calif San Francisco, Div Gen Internal Med, Dept Med, Sch Med, San Francisco, CA 94143 USA
[3] Univ Calif San Francisco, Sch Med, Helen Diller Comprehens Canc Ctr, San Francisco, CA 94143 USA
[4] Univ Calif San Francisco, Sch Med, Dept Epidemiol & Biostat, San Francisco, CA 94143 USA