Zhen Liang1, Qian Huang2, Lan Sheng Zhang3. 1. Department of Obstetrics and Gynecology, Xuzhou Central Hospital, Xuzhou, Jiangsu 221009, P.R. China. / Xuzhou Clinical School of Xuzhou Medical College, Xuzhou, Jiangsu 221000, P.R. China. 2. Department of Radiotherapy, Affiliated Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China. 3. Department of Oncology, the Second Attached Hospital of Xuzhou Medical College, Xuzhou, Jiangsu 221002, P.R. China.