The impact of age at diagnosis on central lymph node metastasis in clinically low-risk papillary thyroid microcarcinoma patients

Background Age is an independent risk factor for central lymph node metastasis (CLNM) in clinically negative lymph node (cN0) papillary thyroid microcarcinoma (PTMC) patients. The objective of this study was to investigate the impact of age on CLNM in clinically low-risk PTMC patients. Methods A retrospective analysis was performed on patients with clinically low-risk PTMC who underwent surgery between January 2016 and December 2018. Logistic regression analysis was used to examine the impact of age on the risk of CLNM. The associations between age and pN1a and the lymph node ratio (LNR) were examined by a restricted cubic spline (RCS) curve with logistic regression models. Results A total of 1352 patients (mean [range] age, 43[18-76] years; 325 males [24.0%]) were enrolled in this study. Logistic regression analysis revealed that age was a significant factor influencing the risk of CLNM (OR 0.95, 95% CI 0.94-0.96; p < 0.001). The RCS curve revealed a significant nonlinear association between age and pN1a status and the LNR. For patients under the age of 55, the risk of CLNM (OR 0.59, 95% CI 0.55-0.65, p < 0.001) and the LNR (beta - 0.23, 95% CI -0.27, -0.19, p < 0.001) significantly decreased as age increased. For patients aged >= 55 years, the risk of LNM (OR 1.03, 95% CI 0.81-1.32; p = 0.79) and the LNR (Beta - 0.03, 95% CI -0.07,0.13, p = 0.54) did not change with age. Conclusions This study confirmed that age was a significant factor influencing the risk and severity of CLNM in patients with low-risk PTMC. The risk and severity of LNM were lowest in patients aged >= 55 years.