Prognostic value of lymph node count from selective neck dissection in oral squamous cell carcinoma.

Unlike the levels of anatomical exploration, there is no consensus on the extent of lymph node dissection, or lymph node count (LNC), during selective neck dissection (SND). The aim of this study was to validate the prognostic impact of LNC on survival and to determine an optimal LNC cut-off value for SND. A retrospective investigation identified 78 patients with a diagnosis of oral squamous cell carcinoma (OSCC) who underwent SND (levels I-III or levels I-IV). LNC and clinicopathological variables were analyzed for any association with survival in Cox proportional hazards models. Based on the receiver operating characteristic curve, a cut-off value of 19 lymph nodes was found to predict overall survival (OS) (area under the curve 0.732, sensitivity 67.8%, specificity 75.0%; P=0.026) and disease-specific survival (DSS) (area under the curve 0.762, sensitivity 68.1%, specificity 77.8%; P=0.011). On Cox regression, LNC (≥19 vs. <19) was the only independent predictor of OS (hazard ratio 5.29, 95% confidence interval 1.39-20.05; P=0.014) and DSS (hazard ratio 6.76, 95% confidence interval 1.40-32.77; P=0.018). Similar results were obtained in the pathologically lymph node-negative subgroup (n=66). Based on the study findings, SND should include 19 or more lymph nodes for a survival benefit.