Lymph node level ratio as a predictor of survival in oral cavity squamous cell carcinoma.

OBJECTIVE: To evaluate whether nodal yields and ratios based on level serves as prognostic indicators in patients with oral cavity squamous cell carcinoma undergoing neck dissection. MATERIALS AND METHODS: A retrospective analysis of 342 patients with oral cavity squamous cell carcinoma treated surgically between 1998 and 2017 were included.Demographics and clinicopathologic data were collated. Disease specific survival and overall survival were analyzed via Kaplan-Meier method and log-rank test as well as univariable and multivariable Cox models. RESULTS: Total nodal yield is associated with improved overall and disease specific survival (p < 0.01). Total positive nodal yield (p < 0.01), positive nodal ratio per level (p < 0.001), and identification of <4 lymph nodes/level (p < 0.001) are associated with worse disease specific survival and overall survival. A ratio of at least 4 lymph nodes/level dissected yields the maximal hazard ratio on for both disease specific and overall survival optimizes the Kaplan-Meier split between survival groups. After controlling for sex, age, margin status, disease stage, extranodal extension, perineural invasion, and lymphovascular invasion as fixed covariates in the Cox models, a nodal level ratio of 4 lymph nodes/level provides hazard ratio (95% CI) of 3.59 (1.69, 7.60); p < 0.0006) for disease free survival and 2.90 (1.54, 5.46; p < 0.001) for overall survival. CONCLUSION: Nodal level ratio of < 4 lymph nodes/level is associated with worse disease specific and overall survival in oral cavity squamous cell carcinoma. This level-specific metric may prove useful qualitatively and in predicting survival in oral cavity cancer with broader utility to address variations in levels of neck dissection performed.