Lymph node ratio as a tool to stratify patients with N1b papillary thyroid cancer.

BACKGROUND

The prognostic significance of lymph node ratio (LNR) in N1b papillary thyroid cancer is unclear. Therefore, the impact of LNR on disease-specific mortality (DSM) and overall survival (OS) in patients with N1b papillary thyroid cancer (PTC) needs to be defined.

METHODS

We used the Surveillance, Epidemiology, and End Results (SEER) database of patients who had undergone thyroidectomy and lymph node dissection. Factors associated with DSM and OS were analyzed and identified using univariate and multivariate Cox proportional risk models. X-tile software was used to find the best cutoff value of LNR. Kaplan-Meier estimates for DSM were plotted for LNR and were compared with the log-rank test. The ROC curve evaluated the validity of the model.

RESULTS

A total of 3223 patients with N1b PTC were identified in the SEER database between 1975 and 2019. The best cutoff value for LNR was 0.6. The multivariate Cox proportional risk model showed that age, race, T3/T4 classification, distant metastasis, extent of surgery, number of metastatic lymph nodes, and LNR > 0.6 were independent risk factors for DSM (all p < 0.05). Age, sex, T4 classification, distant metastasis, extent of surgery, and LNR > 0.6 were independent risk factors for OS (all p < 0.05). The Kaplan-Meier method plotted a cumulative risk curve and showed that patients with LNR > 0.6 had a significantly higher risk of DSM than patients with LNR ≤ 0.6 (p = 0.002).

CONCLUSION

LNR was a powerful predictor of DSM and OS in N1b PTC patients. LNR could be a useful tool for the stratification of PTC patients with lateral neck metastases.