Lymph node ratio in lateral neck is an independent risk factor for recurrence-free survival in papillary thyroid cancer patients with positive lymph nodes

Background The purpose of this study was to explore the impact of the lymph node ratio on prognosis in papillary thyroid cancer patients with lymph node metastasis. Methods Data from papillary thyroid cancer patients with positive nodes who were initially treated at our institution during 2015–2016 were analysed. Univariate and multivariate Cox proportional hazard models were adopted to predict prognostic factors. A receiver operating characteristic (ROC) curve was used to find the best cut-off value of the lymph node ratio (LNR). Kaplan–Meier curves were used to show the relationship between the LNR in the lateral neck and recurrence-free survival. Results The median follow-up time was 64.6 months, and recurrence occurred in 16 of 662 patients (2.27%). Univariate analysis showed that male sex, primary tumour size (>17 mm), visible extrathyroidal extension, LNR in the central neck (>0.5), LNR in the lateral neck (>0.10), and visible extranodal extension were significantly correlated with recurrence-free survival (RFS) ( p < 0.05). Multivariate analysis using the Cox proportional hazards model showed that the LNR in the lateral neck was an independent risk factor for RFS ( p = 0.039; HR 14.76). Conclusion The LNR in the lateral neck was an independent risk factor for recurrence-free survival. For patients with a high lymph node ratio in the lateral neck, more frequent follow-up might be needed.