Maximal lymph nodal diameter in staging system of nasopharyngeal carcinoma

Abstract

Background: The value of maximal lymph nodal diameter in staging system of nasopharyngeal carcinoma (NPC) is not well established.Methods: NPC patients were extracted from SEER database between 2004 and 2016. Overall survival (OS) and cancer-specific survival (CSS) were compared among three groups based on the maximal lymph nodal diameter: ≤3.0 cm, >3.0-6.0 cm, and >6.0 cm. Included patients were randomly divided into training set and validated set with 1:1 ratio. In training set, X-tile plots were created by dividing maximal lymph nodal diameter into three populations. All possible divisions of the maximal lymph nodal diameter were assessed. Two cut-off values were calculated by the X-tile plots in training set. The two cut-off values were evaluated in validated set.Results: The 10-year OS and CSS were different between the three groups. Multivariate regression analysis revealed that maximal lymph nodal diameter >6.0 cm was an independent risk prognostic factor for OS (hazard ratio [HR]=1.91, 95% confidence interval [CI]: 1.51-2.43; P<0.001) and CSS (HR=1.99, 95% CI: 1.51-2.61; P<0.001). The cut-off values of maximal lymph nodal diameter were 1.3 cm and 5.0 cm using X-tile plots in the training set. In the validated set, the maximal lymph nodal diameter >5.0 cm was a risk prognostic factor for OS and CSS.Conclusions: The maximal lymph nodal diameter of 5.0 cm may be a reasonable cut-off value for N stage.