The efficacy and safety of apatinib plus capecitabine in platinum-refractory metastatic and/or recurrent nasopharyngeal carcinoma: a prospective, phase II trial oleh Lin-Quan Tang, Xiao-Yun Li, Zhi-Ming Li, Zhi-Gang Liu, Miao-Zhen Lin, Huan Zhou, Qi-Wen Yu, Jian Zhou, Chong Zhao, Ze-Bin Chen, Xi-Cheng Wang, Jia-Yu Peng, Qiu-Yan Chen, Wen-Feng Fang, Yun-Peng Yang, Bei Zhang, Liang-Ping Xia, Pi-Li Hu, Wei-Han Hu, Yi-Jie Li, Hai-Qiang Mai, Xiu-Yu Cai