Purpose: The delineation of intermediate risk nodal regions (CTVn2) and low-risk nodal regions (CTVn3) base on the correlation analysis between neck node levels of NPC has not been reported. We aim to analyze the correlations between different neck node levels in 960 cases of NPC, and to provide preliminary suggestions for clinical target volume (CTV) delineation of NPC base on the correlation analysis.
Methods and materials: We retrospectively analyzed the records of 960 NPCs in our institution from 2011 to 2019. Diagnostic head and neck CTs and MRIs were reviewed. The involvements of nodal levels were evaluated according to the 2013 updated guidelines. The correlations between different levels were studied using Chi-square test and logistic regression model.
Results: The top four levels with the highest rate of lymph node metastasis were VIIa(86.35%), IIb(84.06%), IIa(62.29%), and III(47.29%). Correlation analysis showed that lymph node metastasis in level Ib was correlated with levels IIa and III. Level IIa was correlated with levels Ib, IIb, III, and Va. Level IIb was correlated with levels IIa, III, Va, and VIIa. Level III was correlated with levels IIa, IIb, IVa, Va, Vb, VIIa, and T stage. Level IVa was correlated with levels III, IVb, and Va. Level IVb was only correlated with level IVa. Level Va was correlated with levels IIb, III, IVa, Vb, and posterior to level V (PLV region). Level Vb was correlated with levels III, Va, Vc, and PLV region. Level Vc was correlated with levels IVb, Vb, and PLV region. Level VIIa was correlated with levels IIb and III. Level VIIb had no correlations with other levels. Level VIII was correlated with levels Ib and IVb. The PLV region was correlated with levels Va, Vb, and Vc. All the above P values were <0.05.
Conclusions: This study recommends setting the related levels as CTVn2 and the unrelated levels as CTVn3. The levels of nodal spread are different in NPC patients, this study reflects the principle of individualized CTV delineation.
Keywords: Correlation analysis; Lymph node metastasis; Nasopharyngeal carcinoma (NPC); Neck node levels.
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