Is 55 years an optimal age cutoff point for clinical staging in T1 papillary thyroid cancer?

[BACKGROUND] This study aims to determine the optimal age cutoff for T1 papillary thyroid cancer (PTC), with a particular focus on the T1a and T1b subgroups.

[METHODS] A retrospective review of electronic medical records was conducted to identify patients who underwent thyroidectomy at our institution from January 2013 to December 2018.

[RESULTS] The study cohort consisted of 2,862 patients, including 765 men (26.7 %) and 2,097 women (73.3 %). Survival analysis demonstrated significantly poorer recurrence-free survival (RFS) in patients aged ≥55 years (p < 0.001). Patients were stratified into T1 (tumor size ≤2 cm, n = 2,328) and non-T1 (tumor size >2 cm, n = 534) subgroups. Among the non-T1 subgroup, older patients exhibited significantly inferior RFS, consistent with the overall cohort (p < 0.001). However, this difference was not observed in the T1 subgroup (p = 0.079). Within the T1 PTC subgroup, significant differences were identified between T1a and T1b patients concerning gender distribution, tumor size, clinical lymph node-positive status (cN1), total thyroidectomy, bilaterality, presence of Hashimoto's thyroiditis, central lymph node metastasis, lateral lymph node metastasis, and radioiodine treatment (all p < 0.05). Further analysis indicated that when stratified by an age cutoff of 65 years, the prognosis for T1b patients was statistically significant (p = 0.018), whereas the prognosis for T1a patients was not statistically significant (p = 0.64).

[CONCLUSION] The clinicopathologic characteristics of T1b patients differ significantly from those of T1a patients. Age may not be a critical factor in the prognostic staging system for T1a PTC patients, whereas 65 years appears to be a more appropriate age cutoff for T1b patients.