Xijing Hospital of Digestive Diseases, Fourth Military Medical University, Xian, China. Department of Radiotherapy, Xijing Hospital, Fourth Military Medical University, Xian, China. Division of Gastroenterology, Department of Medicine, Sepulveda Ambulatory Care Center, Veterans Affairs Greater Los Angeles Healthcare System, 16111 Plummer Street, North Hills, California, USA; David Geffen School of Medicine at UCLA, 10833 Le Conte Avenue, Los Angeles, California, USA. Department of Nursing, Fourth Military Medical University, Xian, China.