Sintilimab in Combination With Chemoradiotherapy in High-risk Locoregionally-advanced Nasopharyngeal Carcinoma

Patients will receive 3 cycles of induction chemotherapy with gemcitabine and cisplatin and concurrent cisplatin-radiation plus Sintilimab, and then receive 11 cycles of Sintilimab after intensity-modulated radiotherapy (IMRT). All patients will receive IMRT. Sintilimab will begin on day 1 of induction chemotherapy and continue every 3 weeks for 17 cycles.