GP Combined With Nimotuzumab and Sintilimab as Induction Therapy for Nasopharyngeal Carcinoma

The goal of this clinical trial is to learn if the regimen of gemcitabine, cisplatin combined with nimotuzumab and sintilimab works to treat locally advanced nasopharyngeal carcinoma before chemoradiotherapy. It will also learn about the safety of the regimen. The main questions it aims to answer are: * Does the regimen increase the number of participants who has a significant tumor shrinkage? * What medical problems do participants have when taking the regimen? Researchers will evaluate the safety and efficacy of the regimen. Participants will: * Take the regimen every 21 days, for twice. * Visit the clinic weekly for drug administration, checkups and tests. * Keep a diary of their symptoms.