Endocrine Abstracts

Background: To date, no staging system has been related to the number of metastatic lymph node or lymph node ratio. Lymph node ratio (LNR) was defined as the number of metastatic LNs divided by the total number of LNs dissected. The purpose of this study was to determine how central LNR had a prognostic value to predict recurrence in N1b papillary cancer.

Methods: This study included 331 patients who underwent total thyroidectomy with lateral neck dissection for N1b papillary thyroid cancer at Seoul St. Mary’s Hospital between January 2012 and December 2017. The mean follow-up duration was 82.1 ± 20.4 months. Hazard ratios of the cut-off LNR values for cancer recurrence were calculated for relevant covariates using multivariate Cox regression analyses. Kaplan-Meier analyses were also utilized to assess the effects of estimated LNR cut-off values on disease-free survival (DFS).

Results: The patients enrolled was divided into two groups according to central lymph node ratio, and the cut-off value of 0.56 was determined by ROC curve. Age, sex, tumor size, lymphatic invasion, vascular invasion, the number of positive LNs, T stage, TNM stage, and recurrence were factors that statistically relevant to central LNR. Multivariate Cox regression analyses revealed that central lymph node ratio higher than 0.56 was an independent prognostic factor for recurrence in N1b papillary thyroid cancer (hazard ratio [HR]: 6.177, 95% confidence interval [CI]: 1.763-21.639, P = 0.004). In addition, tumor size was independently prognostic for recurrence (hazard ratio [HR]: 1.951, 95% confidence interval [CI]: 1.140-3.340, P = 0.015). Kaplan-Meier analyses demonstrated that higher LNR of central compartment with cut-off value of 0.56 reduced disease-free survival (log-rank P < 0.001).

Conclusion: Central LNR was an independent prognostic factor in N1b PTC patients.

Keywords: Papillary thyroid cancer, central lymph node, lymph node ratio, Disease-free survival