鼻咽癌是我国南方特别是广东地区的高发肿瘤,绝大多数病理类型为低分化癌,其易浸润性生长及远处转移的生物学特征尤为显著,特别是颈部淋巴结的转移率可高达78.9%[1]。随着三维适形放疗(3D-CRT)及适形调强放疗(IMRT)在临床上的应用,更精确地控制放射剂量的分布成为可能。对鼻咽 Nasopharyngeal carcinoma is a highly malignant tumor in southern China, especially in Guangdong. Most of the pathological types are poorly differentiated carcinoma. The biological characteristics of nasopharyngeal carcinoma are particularly prominent in its easy infiltrative growth and distant metastasis. In particular, the metastatic rate of cervical lymph nodes can be up to 78.9% [1]. With the clinical application of three-dimensional conformal radiotherapy (3D-CRT) and conformal IMRT, it is possible to control the distribution of radiation dose more accurately. On the nasopharynx