Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, Arizona. University of Arizona Cancer Center, Tucson, Arizona. jacobse@email.arizona.edu. Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, Arizona. University of Arizona Cancer Center, Tucson, Arizona. Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, Arizona. Department of Family and Preventive Medicine, University of California San Diego, La Jolla, California. Mel and Enid Zuckerman College of Public Health, University of Arizona, Tucson, Arizona. University of Arizona Cancer Center, Tucson, Arizona. University of Arizona Cancer Center, Tucson, Arizona. Department of Basic Medical Sciences, University of Arizona College of Medicine, Phoenix, Arizona. School of Mathematical and Natural Sciences, Arizona State University, Phoenix, Arizona.