Reducing High Risk Primary Tumor Clinical Target Volumes (CTVp1) in Non-metastatic Nasopharyngeal Carcinoma

1. histologic confirmation of nonkeratinizing nasopharyngeal carcinoma(WHO II-III);
2. newly diagnosed stage I to IVa according to the American Joint Committee on Cancer-Union for International Cancer Control 8th edition stage-classification system
3. nasopharyngeal mass confined to one side of nasopharynx and did not exceed the midline(the line between the nasal septum and the midpoint of spinal cord/medulla) detected by electronic nasopharyngoscope (ENS) and magnetic resonance imaging (MRI). Pathological biopsy was recommended if it was unclear whether tumor invaded the contralateral side radiographically.
4. planned to receive curative IMRT, Chemotherapy drugs should be administered according to Chinese Society of Clinical Oncology (CSCO) guidelines depending on the TNM stage;(T1N0: No chemotherapy required;T2N0：No chemotherapy or concurrent cisplatin chemoradiotherapy if there are adverse prognostic indicators such as Epstein-Barr virus (EBV) DNA>4000 copies，node >3cm or with extranodal extension;T1-2N1: concurrent cisplatin chemoradiotherapy;T3N0: concurrent cisplatin chemoradiotherapy; stage III-Iva: platinum-based neoadjuvant chemotherapy+ concurrent cisplatin chemoradiotherapy+/-metronomic capecitabine therapy )
5. no previous treatment for cancer；
6. a Karnofsky performance-status score of at least 70 (on a scale from 0 to 100, with lower scores indicating greater disability);
7. between 18 and 70 years old;
8. adequate hematologic, renal, and hepatic function: Adequate marrow function: WBC count ≥ 3×10E9/L, NE count ≥ 1.5×10E9/L, HGB ≥ 90g/L, PLT count ≥ 100×10E9/L;Adequate liver function: ALT and AST ≤ 2.5×ULN, TBIL ≤ 2.0×ULN;Adequate renal function: BUN and CRE ≤ 1.5×ULN , endogenous creatinine clearance ≥ 60ml/min (Cockcroft-Gault formula);
9. Patients must be informed of the investigational nature of this study and give written informed consent.

Exclusion Criteria:

1. receipt of treatment with palliative intent;
2. receipt of previous treatment (radiotherapy, chemotherapy, or surgery [except diagnostic procedures]) to the nasopharynx;
3. had disease progress after neoadjuvant chemotherapy in local advantage NPC
4. presence of distant metastasis;
5. Keratinized squamous cell carcinoma or basal cell like squamous cell carcinoma;
6. Prior malignancy except adequately treated non-melanoma skin cancer, in situ cervical cancer, and papillary thyroid carcinoma;
7. Have New York Heart Association (NYHA) class 3 or 4, unstable angina, myocardial -infarction within 1 year, or clinically meaningful arrhythmia that requires treatment;
8. lactation or pregnancy;
9. Any other condition including Mental disorder,drug or alcohol addition;do not have full capacity for civil acts.