a clear trendP =0.0527
Patients were divided into three subgroups according to dynamic changes of EBV-DNA status: EBV-DNA persistently negative group (PNG, 24/58), EBV-DNA persistently positive group (PPG, 16/58), and EBV-DNA transformed from positive to negative group (TNG, 18/58); among the three groups, PPG had a clear trend toward worse PFS and OS ( P =0.0527 and P =0.0139, respectively) (Figure 1E, 1F).