Plasma Epstein-Barr virus DNA level strongly predicts survival in metastatic/recurrent nasopharyngeal carcinoma treated with palliative chemotherapy. - An, Xin; Wang, Feng-Hua; Ding, Pei-Rong; Deng, Ling; Jiang, Wen-Qi; Zhang, Li; Shao, Jian-Yong; Li, Yu-Hong (Cancer (0008543X), 2011)