Reduced vs Conventional Dosage Intensity-modulated Radiotherapy for Chemotherapy-sensitive Stage II-III Nasopharyngeal Carcinoma

"1. Gemcitabine plus cisplatin induction chemotherapy: gemcitabine is injected intravenously at the dose of 1000 mg/m2 on the 1st and 8th day (within 30 minutes) for 3 cycles; cisplatin is injected intravenously at the dose of 80 mg/m2 on the 1st day, for 3 cycles. 1 cycles per 3 weeks.~2. Concurrent cisplatin chemotherapy: cisplatin is given at a dose of 100 mg/m2 via a continuous intravenous infusion during radiotherapy and starts on the 1st day of radiotherapy for 2 cycles. 1 cycles per 3 weeks.~3. IMRT: PTVnx：63.6Gy/30Fr/2.12Gy; PTVnd：63.6Gy/30Fr/2.12Gy; PTV1：54Gy/30Fr/1.8Gy; PTV2：49.2Gy/30Fr/1.64Gy"

"1. Gemcitabine plus cisplatin induction chemotherapy: gemcitabine is injected intravenously at the dose of 1000 mg/m2 on the 1st and 8th day (within 30 minutes) for 3 cycles; cisplatin is injected intravenously at the dose of 80 mg/m2 on the 1st day, for 3 cycles. 1 cycles per 3 weeks.~2. Concurrent cisplatin chemotherapy: cisplatin is given at a dose of 100 mg/m2 via a continuous intravenous infusion during radiotherapy and starts on the 1st day of radiotherapy for 2 cycles. 1 cycles per 3 weeks.~3. IMRT: PTVnx：69.96Gy/33Fr/2.12Gy; PTVnd：69.96Gy/33Fr/2.12Gy; PTV1：59.4Gy/33Fr/1.8Gy; PTV2：54Gy/33Fr/1.64Gy"