Liquid biopsy posttreatment surveillance in endemic nasopharyngeal carcinoma: a cost-effective strategy to integrate circulating cell-free Epstein-Barr virus DNA oleh Chen-Fei Wu, Li Lin, Yan-Ping Mao, Bin Deng, Jia-Wei Lv, Wei-Hong Zheng, Dan-Wan Wen, Jia Kou, Fo-Ping Chen, Xing-Li Yang, Si-Si Xu, Jun Ma, Guan-Qun Zhou, Ying Sun