Abstract
Background: The 2015 American Thyroid Association guidelines recommend the maintenance of serum thyroid stimulating hormone (TSH) levels ≤2 mIU/L in patients with low-risk papillary thyroid carcinoma (PTC) who underwent lobectomy; however, the evidence is insufficient. We investigated the association between maintaining the TSH status at ≤2 mIU/L and tumor recurrence in patients with low-risk PTC who underwent lobectomy through a 5-year landmark analysis. Methods: Between 2010 and 2016, 662 patients with low-risk PTC were included. The postoperative TSH status was determined using the 'TSH > 2 ratio', which was calculated using the TSH test results during the 5-year follow-up. The optimal cutoff value of 'TSH > 2 ratio' for tumor recurrence was determined using a receiver operating characteristic curve analysis. Recurrence-free survival (RFS) was compared between the groups using Kaplan-Meier and Cox proportional hazard regression analyses. Results: Patients with 'TSH > 2 ratio' > 0.1833 (n = 498) had a worse RFS outcome compared to patients with 'TSH > 2 ratio' ≤ 0.1833 (n = 164; p < 0.001). 'TSH > 2 ratio' > 0.1833 was a significant risk factor for tumor recurrence after the 5-year landmark (hazard ratio: 4.795, 95% confidence interval: 2.102-10.937, p < 0.001). Conclusions: Maintaining TSH levels ≤ 2 mIU/L below a certain percentage among the total TSH tests during the 5-year follow-up period has a negative impact on tumor recurrence.