Lymph Node Ratio in HPV-Associated Oropharyngeal Cancer: Identification of a Prognostic Threshold

Objective: To evaluate the utility of lymph node ratio (LNR) as a prognostic factor for survival and recurrence in surgically treated patients with human papillomavirus (HPV)-related oropharyngeal squamous cell carcinoma (OPSCC). Study Design: Retrospective cohort study. Methods: In this retrospective cohort study of a tertiary healthcare system in a major metropolitan area, we reviewed 169 consecutive patients with HPV-related OPSCC treated using transoral robotic surgery. Univariable and multivariable Cox proportional hazards regression analysis with stratified models were used to compare LNR with other traditional clinicopathologic risk factors forrecurrence and survival. An LNR cutoff was found using the minimal P approach. Results: Multivariable Cox regression models showed that each additional percentage increase in LNR corresponded to an adjusted hazard ratio (HR) of 1.04 (confidence interval [CI] 1.02–1.07). LNR was more significant when adjusted for adequate lymph node yield of ≥ 18 nodes (HR 5.05, 95% confidence interval [CI] 1.38–18.47). The minimal P generated cutoff point at LNR ≥ 17% demonstrated a HR 4.34 (95% CI 1.24–15.2) for disease-free survival. Conclusion: For HPV-related OPSCC, continuous LNR and an LNR threshold of 17% could be helpful in identifying recurrent disease in addition to measures such as lymph node number alone.