Relationship between circulating anti-thyroglobulin antibodies (TgAb) and tumor metabolism in patients with differentiated thyroid cancer (DTC): prognostic implications

Purpose TgAb have been proposed as tumor markers in DTC. Recent evidence links TgAb levels with DTC aggressiveness. We aimed to evaluate the relationship between TgAb and tumor glucose metabolism in DTC patients. Methods Seventy-one DTC patients who underwent F-18-FDG PET/CT were included. According to TgAb value and trends, patients were divided into TgAb positive (TgAb+) or negative (TgAb-) as well as in patients with increasing (Inc-TgAb) or decreasing (Dec-TgAb) trend. On the basis of the results of FDG-PET, post-therapy 13II and Tg levels, patients were divided into two groups according to the evidence (ED) or absence (NED) of disease. ED patients were further divided into three subgroups: 1. radioiodine avid with positive F-18-FDG PET/CT (PET+/13II+), 2. radioiodine refractory with positive F-18-FDG PET/CT (PET+/131I-) and 3. radioiodine avid with negative F-18-FDG PET/CT (PET-/13II+). Mean-SUV of FDG-avid lesions was assessed and averaged each patient (SUVmean-pt). T test was performed to assess the difference between SUVmean in TgAb-, TgAb+ and in Inc-TgAb and Dec-TgAb subgroups. Difference in TgAb between ED and NED patients as well as between ED patients and PET+/13II+, PET+/13II-and PET-/13II+ subgroups was compared. Results SUVmean was significantly higher in Inc-TgAb with respect to Dec-TgAb subgroup (5.2 +/- 1.5 vs. 2.9 +/- 1.1, p < 0.05). TgAb were higher only in the ED PET+/13II+ subgroup with respect to NED patients (p < 0.01). Conclusions The relationship between higher tumor metabolism and trend of TgAb supports a prognostic relevance of TgAb in DTC patients. Significantly higher TgAb in radioiodine avid tumors with positive F-18-FDG PET/CT further testify the role of TgAb as surrogate tumor marker in DTC.