1. Department of Respiratory Medicine, Public Health Clinical Center of Chengdu, Chengdu, Sichuan 610041, P.R. China
2. Department of Oncology, People's Hospital of Leshan, Leshan, Sichuan 614000, P.R. China
3. Department of Oncology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu 221002, P.R. China