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Background: The optimal serum thyrotropin (TSH) level for postlobectomy papillary thyroid carcinoma (PTC) patients is unclear. The objective of this study was to examine the association of TSH and recurrence in postlobectomy patients. Methods: Patients who underwent lobectomy for PTC in a single tertiary hospital from January 2000 to December 2014 were enrolled. The mean TSH of a patient was calculated based on each serum TSH value during follow-up. The reference range of serum TSH was 0.5–4.0 mU/L. Univariate and multivariable analyses were performed with Cox proportional hazards models. Restricted cubic spline (RCS) functions were used to model relationships between mean TSH and recurrence-free survival (RFS). Results: A total of 2297 patients (median age 42 years; 1750 (76.2%) female) were analyzed. Mean TSH below (≤0.5mU/L), in the lower half (0.6–2 mU/L), in the upper half (2.1–4 mU/L), and above (>4 mU/L) the reference range were observed in 668 (29.1%), 1162 (50.6%), 345 (15.0%), and 122 (5.3%) patients, respectively. According to the Cox model and RCS, no association was observed between mean TSH and RFS in the whole cohort, low-risk group and intermediate- to high-risk groups (adjusted p = 0.4737, 0.9314, 0.1859, adjusted p for nonlinear = 0.4589, 0.8622, 0.3010). The only RFS difference observed in the stratified univariate analysis was between patients with mean TSH in the lower half (0.6–2 mU/L, n = 659) and above the reference range (>4 mU/L, n = 68) in the intermediate- to high-risk group (10-year RFS by Kaplan–Meier 84.4% vs. 69.4%, log rank p = 0.011). Conclusions: Mean serum TSH levels are not associated with recurrence. A normal TSH reference range is recommended for postlobectomy PTC patients. [ABSTRACT FROM AUTHOR]

Background: The value of serum thyroglobulin/antithyroglobulin (Tg/antithyroglobulin antibody [ATg]) for papillary thyroid carcinoma (PTC) surveillance after lobectomy was investigated. We aimed to examine the association between postlobectomy serum Tg/ATg and PTC structural recurrence and define applicable values for stratification. Methods: PTC patients who underwent lobectomy with adequate serum Tg/ATg data during 2000–2014 were selected. Predictive classifiers of recurrence using random forest were established combining different variables related to serum Tg (ATg-negative patients) or ATg (ATg-positive patients). Cutoff values were determined with receiver operating characteristic curves when applicable. Kaplan–Meier curve and Cox regression were performed to examine the predictive value of elevated Tg/ATg. Results: Of 1451 patients enrolled, 66 (6.3%) and 26 (6.5%) patients in the ATg-negative group (n = 1050) and ATg-positive group (n = 401) developed recurrence. The established classifier of serum Tg (n = 1050) showed a favorable association with recurrence (AUC = 0.81), while serum ATg did not (AUC = 0.72). The optimal cutoff values of the first Tg (FTg, measured 6–12 months after lobectomy) and last Tg (LTg, measured most recently) were 5.3 and 11.0 ng/mL, respectively. Elevated LTg patients had significantly higher recurrence rates than normal LTg patients (23.5% vs. 4.4%, p < 0.05). Patients with elevated FTg had significantly lower recurrence-free survival rates than patients with normal FTg in all ATg-negative patients, low-risk patients, and intermediate- to high-risk patients (according to the American Thyroid Association initial risk stratification) (n = 1050, 583, and 467, all p < 0.05). Multivariate analysis indicated patients with elevated FTg had twice the recurrent risk compared with those with normal FTg (hazard ratio = 2.052). Conclusions: Postlobectomy serum Tg has favorable value for predicting recurrence in PTC patients, and reasonable thresholds could identify patients at higher risk for recurrence during follow-up. [ABSTRACT FROM AUTHOR]