1. Department of Otorhinolaryngology, Qilu Hospital, Shandong University, Key Laboratory of Otolaryngology, NHFPC (Shandong University), Jinan 250012, P. R. China
2. Department of Head and Neck Surgery, Houston, TX 77030, USA
3. Department of Otorhinolaryngology, Shanghai Ninth People's Hospital, Shanghai Jiaotong University, School of Medicine, Shanghai 200011, P. R. China
4. Epidemiology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA