Adebrelimab and Chemoradiotherapy in High-risk LANPC

"Drug: Adebrelimab Adebrelimab 1200mg will be given every 3 weeks for 3 cycles in induction chemotherapy and for 9 cycles in adjuvant chemotherapy, started on day 1 of induction chemotherapy and adjuvant chemotherapy, respectively.~Other Names:~PD-L1 antibody~Drug: Gemcitabine Gemcitabine 1g/m2, d1 \& 8 of every cycle, every 3 weeks for 3 cycles before radiation.~Other Names:~GEM~Drug: Cisplatin Induction cisplatin 80mg/m2, every 3 weeks for 3 cycles before radiation; Concurrent cisplatin 100mg/m2, every 3 weeks for 2 cycles during radiation~Other Names:~DDP~Radiation: Intensity-modulated radiotherapy Definitive intensity-modulated radiotherapy (IMRT) of 6996cGy will be given in 33 fractions.~Other Names:~IMRT"