Role of Thyroglobulin Doubling Time in Differentiated Thyroid Cancer and Its Relationship with...

Aim of this study was to investigate the relationship between thyroglobulin doubling time (TgDT) and basal risk factors and metabolic parameters derived from ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in differentiated thyroid cancer (DTC). An analysis of 95 DTC patients who had rising serum thyroglobulin (Tg) levels under levothyroxine (LT4) suppression after radioiodine therapy was made. TgDT was calculated for 28/95 patients. The relationship between TgDT and basal demographic and histopathologic risk factors, preablative Tg, and antithyroglobulin antibody (ATg) levels and metabolic parameters was analyzed. In 28 patients (15M, 13F, mean age: 52.6 ± 17.6) that TgDT could be calculated, ¹⁸F-FDG PET/CT was positive in 12 patients. Median TgDT was lower in ¹⁸F-FDG PET/CT positive patients compared to the negative cases (p < 0.05). Patients with skeletal metastasis or local recurrence had a shorter DT compared to the patients with lung metastasis. TgDT was correlated with peak standardized uptake value (SUV_peak) (p < 0.05). Maximum standardized uptake value (SUV_max) was correlated with tumor size (p < 0.05) and mean standardized uptake value (SUV_mean) with tumor size and vascular invasion (p < 0.05). Median SUV_max and SUV_mean were higher in follicular cancer or poor histological variants of papillary DTC compared to papillary cancer classical variant patients TgDT may be predictive of a positive ¹⁸F-FDG PET/CT in DTC. Skeletal metastasis and local recurrence are related to shorter TgDT. Greater tumor size, vascular invasion, and follicular cancer or poor variants of papillary carcinoma are related with higher SUV_max and SUV_mean. Larger scale studies are needed to confirm results and to calculate a possible cutoff of TgDT for a positive ¹⁸F-FDG PET/CT study.