1. Gansu Provincial Academy of Medical Sciences, Gansu Provincial Cancer Hospital, Lanzhou, People's Republic of China.
2. School of Life Sciences, Lanzhou University, Lanzhou, China.
3. Department of Chronic Disease Epidemiology, School of Public Health, School of Medicine, Yale Cancer Center, Yale University, New Haven, Connecticut.
4. Institute of Urology, The Second Hospital of Lanzhou University, Lanzhou, China.