To analyze the long-term results and toxicities of the reducing clinical target volume (CTV) delineation method in early-stage nasopharyngeal carcinoma (NPC) patients treated with intensity modulated radiation therapy (IMRT).

The investigators designed a prospective phase II study for early-stage NPC patients, and proposed a reasonable delineation method of reducing CTV according to the clinical characteristics and tumor infiltration patterns, performing therapeutic dose to tumor and prophylactic dose to CTV while protecting as much normal tissues as possible, in order to ensure a long-term survival with good quality of life.

Inclusion Criteria:

1. histologically confirmed NPC (WHO II-III)
2. stage I-IIb according to the 6th AJCC/UICC
3. no previous treatment for NPC
4. between 18 and 70 years old
5. KPS ≥ 80 scores
6. adequate organ function (white blood cell ≥ 4.0×109/L; absolute neutrophil count ≥ 1.5×109/L; hemoglobin ≥ 100g/L; platelet count ≥ 100×109/L; total bilirubin, aspartate aminotransferase and alanine aminotransferase ≤ 1.5X upper limit normal; and creatinine clearance rate ≥ 30 mL/min)

Exclusion Criteria:

1. fine-needle aspiration biopsy, incisional or excisional biopsy of neck lymph node, or neck dissection prior IMRT
2. disease progression during IMRT
3. presence of distant metastasis
4. pregnancy or lactation
5. previous malignancy or other concomitant malignant disease