The role of lymph node level ratio in predicting prognosis and the benefits of postoperative radiotherapy in patients with pathological N1 stage head and neck squamous cell carcinoma

Objective: To analyze the role of lymph node level ratio (LNLR) in predicting prognosis and the benefits of postoperative radiotherapy (PORT) in patients with pathological N1 (pN1) head and neck squamous cell carcinoma (HNSCC). Methods: Patients with pN1 HNSCC from January 2011 to February 2021 were included. Patients were grouped by the LNLR, lymph node yield (LNY), and lymph node ratio (LNR) and were analyzed with the Kaplan-Meier method and multivariate Cox model. Results: This study identified 310 patients. Time-dependent receiver operating characteristic analyses showed superior prognostic ability for LNLR in comparison with LNY and LNR. Patients with an LNLR <= 5.25 had the worst survival. Multivariate regressions demonstrated larger hazard ratios (HRs) and a higher concordance index for the LNLR model versus the LNY and LNR models. The HRs (95 % confidence interval) for a LNLR <= 5.25 were 2.46 (1.71-3.54, p < 0.001) for DFS, 1.95 (1.38-2.75, p < 0.001) for OS, 2.25 (1.53-3.29, p < 0.001) for DSS. Furthermore, postoperative radiotherapy-related significant improvement in survival was observed exclusively in the LNLR <= 5.25 subgroup. Conclusion: The LNLR is a more robust quality indicator for neck dissection. An LNLR of <= 5.25 significantly compromises survival and indicates the need for PORT in patients with pN1 HNSCC.