[1] Univ So Calif, Sch Med, Dept Prevent Med, Kenneth Norris Jr Comprehens Canc Ctr, Los Angeles, CA 90033 USA
[2] Int Agcy Res Canc, Unit Field & Intervent Studiews, F-69372 Lyon, France
[3] NCI, Radiat Epidemiol Branch, Rockville, MD USA
[4] Mario Negri Inst Pharmacol Res, Lab Gen Epidemiol, Milan, Italy