1. Department of Medicine Oncology, The Fifth People's Hospital of Qinghai Province, Xining, Qinghai 810007, P.R. China
2. Department of Medicine Oncology, The Affiliated Hospital of Qinghai University, Xining, Qinghai 810016, P.R. China
3. Department of Science and Education, The Fifth People's Hospital of Qinghai Province, Xining, Qinghai 810007, P.R. China
4. Department of Oncology, The Second Affiliated Hospital of Xi'an Jiaotong University, Xi'an, Shaanxi 710061, P.R. China
5. Department of Respiratory Medicine, Shaanxi Provincial Corps Hospital of Chinese People's Armed Police Force, Xi'an, Shaanxi 710054, P.R. China