Is Age ≥ 55 years an optimal cutoff point among patients with differentiated thyroid Microcarcinoma? a preliminary study.

Purpose: Age ≥ 55 years is regarded as a pivotal component of TNM stage classification in differentiated thyroid carcinoma (DTC). However, whether this cutoff point is still adaptable for differentiated thyroid microcarcinoma (DTMC) is rarely investigated.

Methods: We reviewed and analyzed the data of DTC patients aged ≥ 55 years from the Surveillance, Epidemiology, and End Results (SEER) database. Univariate and multivariate Cox regression analyses were used to determine the potential risk factors of cancer-specific survival (CSS) in DTMC patients aged ≥ 55 years. The Kaplan-Meier survival curves were used to estimate CSS probability. Receiver operating characteristic (ROC) curves were used to analyze the best age cutoff point for DTMC.

Results: Among the DTMC patients, there was no significant difference in the 1-, 3-, 5-, and 7-year CSS probability between the 55-59 years and 60-64-years subgroup (p = 0.72). The ROC curves indicated that 65 years, 65 years, and 64 years were the cutoff age point of 3-, 5-, and 7-year CSS probability in DTMC patients, respectively. Besides, N1b (Hazard ratio (HR) = 3.90, 95% Confidence interval (CI): 2.01-7.57; p < 0.001), extrathyroidal extension (HR = 2.53, 95 %CI: 1.39-4.62; p = 0.002), and M1 (HR = 11.42, 95 %CI: 5.04-25.90; p < 0.001) were the independent risk factors in CSS of DTMC patients.

Conclusions: Our results suggested age at diagnosis ≥ 55 years is not the best cutoff point in stratifying the stage of the DTMC patients. On the contrary, those patients aged above 65 years have a significantly lower probability of CSS, which perhaps should be taken into consideration for treatment decision-making.