Nasopharyngeal carcinoma (NPC) is a unique head and neck cancer characterized by an extremely unbalanced global distribution. The highest incidence is observed in endemic regions, such as southern China and Southeast Asia, with an age-standardized rate of 3.0 per 100,000 in China to 0.4 per 100,000 in Caucasian populations. The fast progress of modern imaging and the application of intensity-modulated radiotherapy (IMRT) has improved the local control rate significantly. Distant metastasis has become the major cause of treatment failure.~The 2018 National Comprehensive Cancer Network (NCCN) guideline recommends concurrent chemoradiotherapy (CCRT) ± induction chemotherapy (IC)/adjuvant chemotherapy (AC) as the standard treatment for stage II-IVa disease (category 2A). While it is worth noting that there is extensive heterogeneity among patients with NPC, and even among patients with the same disease stage, the risk of relapse varies. More importantly, patients can have differing sensitivity to RT and chemotherapy. The abovementioned reasons result in over-treatment in some patients with relatively low relapse risk; intensive treatments lead to unnecessary toxicities, and greatly affect quality of life (QoL). On the other hand, the current treatment strategy may be not optimal for patients with high relapse risk or who are not sensitive to traditional chemoradiotherapy. Therefore, there is an urgent need for identifying and applying promising biomarkers, real-time monitoring of patient responses to treatment, predicting relapse risk, and guiding real-time treatment adaptation for individualized therapy.~The investigators aim to investigate whether incorporating on-treatment EBV DNA surveillance for monitoring tumor responses to treatment and for guiding individuliased treatment adaptation can improve prognosis in nasopharyngeal carcinoma patient . For patients with detectable EBV DNA after one cycle of IC, which then drops to undetectable levels during the following IC cycles (intermediate responders/intermediate relapse risk), the investigators aim to investigate whether additional adjuvant metronomic capecitabine would benefit this subgroup. For patients with detectable EBV DNA after three cycles of IC or with EBV DNA bounce during the induction phase (insensitive to IC/high relapse risk), the investigators aim to investigate whether concurrent administration of anti-PD-1 therapy during the following treatment phases (including concurrent phase and adjuvant phase) can benefit this subgroup.
The investigators aim to investigate whether incorporating on-treatment EBV DNA surveillance for monitoring tumor responses to treatment and for guiding individuliased treatment adaptation can improve prognosis in nasopharyngeal carcinoma patient . For patients with detectable EBV DNA after one cycle of IC, which then drops to undetectable levels during the following IC cycles (intermediate responders/intermediate relapse risk), the investigators aim to investigate whether additional adjuvant metronomic capecitabine would benefit this subgroup. For patients with detectable EBV DNA after three cycles of IC or with EBV DNA bounce during the induction phase (insensitive to IC/high relapse risk), the investigators aim to investigate whether concurrent administration of anti-PD-1 therapy during the following treatment phases (including concurrent phase and adjuvant phase) can benefit this subgroup.