1. Department of Epidemiology and Biostatistics; Memorial Sloan-Kettering Cancer Center, New York; New York 10065 U.S.A.
2. Division of Cancer Etiology, Department of Population Sciences; Beckman Research Institute, City of Hope; Duarte, California 91010 U.S.A.
3. Department of Pathology; USC/Norris Comprehensive Cancer Center; Los Angeles, California 90033 U.S.A.