Correlation analysis of neck node levels in 709 cases of nasopharyngeal carcinoma

Background and purpose: The research on radiotherapy clinical target volume (CTV) delineation based on the correlation analysis between neck node levels of nasopharyngeal carcinoma has not been reported. We retrospectively analyzed 709 cases of nasopharyngeal carcinoma with cervical lymph node metastasis, and aimed to provide a preliminary opinion for the CTV delineation of nasopharyngeal carcinoma based on the correlation analysis of node involvement in each neck node level. Methods: Based on the 2013 updated guideline of delineation of the neck node levels for head and neck tumors, we analyzed 709 nasopharyngeal carcinoma patients with cervical lymph node metastasis in the General Hospital of Western Theater Command from December 2011 to June 2018. The correlations between different levels were studied using χ 2 test and logistic regression model. Results: The top four node levels with the highest probability of metastasis were level Ⅱb (82.79%), level Ⅶa (82.65%), level Ⅱa (60.50%) and level Ⅲ (43.86%). Correlation analysis showed the lymph node metastasis in level Ⅰb was correlated with level Ⅱa and Ⅲ, level Ⅱa was correlated with level Ⅰb, Ⅱb, Ⅲ, Ⅴa and Ⅴc, level Ⅱb was correlated with level Ⅱa, Ⅲ, Ⅳa, Ⅴa, Ⅴb and Ⅶa, level Ⅲ was correlated with level Ⅱa, Ⅱb, Ⅳa, Ⅴa, Ⅴb, Ⅴc and Ⅶa, level Ⅳa was correlated with level Ⅱa, Ⅱb, Ⅲ, Ⅳb, Ⅴa and Ⅴc, level Ⅳb was correlated with level Ⅳa, level Ⅴa was correlated with level Ⅱb, Ⅲ, Ⅳa, Ⅴb and posterior to level Ⅴ (PLV), level Ⅴb was correlated with level Ⅲ, Ⅴa, Ⅴc and PLV, level Ⅴc was correlated with level Ⅱa, Ⅲ, Ⅳa, Ⅴb and PLV, levelⅦa was correlated with level Ⅱb and Ⅲ, and the PLV region was correlated with level Ⅴa, Ⅴb and Ⅴc (all P＜0.05). Conclusion: The lower cervical node involvement is based on the lymph node metastasis of upper levels. The delineation of intermediate risk CTV can be reduced based on the correlation analysis of neck node levels.