The Effect of Positive Cervical Lymph Node Count on Long-Term Survival of Papillary Thyroid Cancer: A Large Population-Based Study.

IntroductionInadequate and conflicting reporting exists regarding the intricate association between positive lymph node (PLN) number and papillary thyroid cancer (PTC) survival. Our aim was to elucidate the relationships between PLN and overall survival in PTC patients using a large population-based study.MethodsData on PTC patients diagnosed between 2004 and 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Proportional hazards regression models with restricted cubic splines (RCS) were employed to examine the associations between them. Multivariable adjusted Cox regression models and sensitivity analyses were conducted to validate the association.ResultsIn total, 44,181 patients with PTC were included (18,148 with and 26,033 without lymph node metastases). After adjusting for covariate effects, patients with node metastases exhibited compromised survival compared to those without (hazard ratio[HR], 1.58; 95% confidence interval [CI], 1.44 to 1.74). In the RCS model, all-cause mortality risk increased rapidly until seven PLN, with a HR of 1.14 (95% CI, 1.11 to 1.17) per increase of one metastatic node but stabilized afterwards (HR, 1.01; 95% CI, 0.98 to 1.05) (P for non-linearity <0.001). Furthermore, multivariate Cox models and sensitivity analyses confirmed similar correlations between the PLN count and overall survival.ConclusionsOur study suggests an evident non-linear association between PLN number and overall survival in PTC patients, suggesting a potential threshold of seven or fewer PLN to have better survival outcome.