1. Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou, P. R. China
2. Sihui Cancer Institute, Sihui, Guangdong, P. R. China
3. Division of Epidemiology, Department of Health Research and Policy, Stanford University School of Medicine, Stanford, CA, USA
4. Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden
5. Department of Epidemiology, Harvard School of Public Health, Boston, MA, USA