1. State Key Laboratory of Oncology in South China Collaborative Innovation Center for Cancer Medicine; Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy Sun Yat‐sen University Cancer Center Guangzhou Guangdong 510060 P. R. China
2. School of Public Health The University of Hong Kong Hong Kong S.A.R. 999077 P. R. China
3. Center for Nasopharyngeal Carcinoma Research Research Grants Council Area of Excellence Scheme The University of Hong Kong Hong Kong S.A.R. 999077 P. R. China
4. Radiation Epidemiology Branch Division of Cancer Epidemiology and Genetics National Cancer Institute, National Institutes of Health Bethesda MD 20892 USA
5. School of Public Health Sun Yat‐sen University Guangzhou Guangdong 510080 P. R. China
6. Wuzhou Red Cross Hospital Wuzhou Guangxi 543002 P. R. China
7. Wuzhou Cancer Center Wuzhou Guangxi 543002 P. R. China
8. Center for Health Sciences Exponent, Inc., Menlo Park, CA, 94025 Department of Epidemiology and Biostatistics University of California San Francisco CA 94143 USA
9. Department of Otolaryngology‐Head and Neck Surgery First Affiliated Hospital of Guangxi Medical University Nanning Guangxi 530021 P. R. China
10. Department of Radiation Oncology Sun Yat‐sen University Cancer Center; State Key Laboratory of Oncology in South China; Collaborative Innovation Center for Cancer Medicine; Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy Guangzhou Guangdong 510060 P. R. China
11. Department of Clinical Oncology The University of Hong Kong Hong Kong S.A.R. 999077 P. R. China
12. Clinical Effectiveness Group Institute of Health and Society University of Oslo Oslo 0316 Norway
13. Department of Medical Epidemiology and Biostatistics Karolinska Institutet Stockholm 17177 Sweden
14. Department of Epidemiology and Health Statistics & Key Laboratory of Ministry of Education for Gastrointestinal Cancer Fujian Medical University Fuzhou Fujian 350122 P. R. China