Thyroid ¹⁸F-fluorocholine uptake in patients with chronic autoimmune thyroiditis

Abstract

Objective

¹⁸F-Fluorocholine ( ¹⁸FCH) PET/CT has high sensitivity for parathyroid adenoma detection and can reliably exclude malignancy in thyroid nodules with indeterminate cytology. Data regarding ¹⁸FCH uptake in chronic autoimmune thyroiditis (CAT) are scarce. We aimed to assess thyroid ¹⁸FCH uptake in CAT with biological and histological correlation.

Methods

This is an ancillary study from the Chocolate trial (NCT02784223) that prospectively enrolled 107 patients planned for thyroid surgery. ¹⁸FCH PET/CT acquisitions were performed 20 and 60 min after injection. ¹⁸FCH uptake in the thyroid gland was assessed by measuring maximum (SUVmax) and mean (SUVmean) standardized uptake values. Thyrotropin, free thyroxine (FT4), thyroid peroxidase antibodies (TPOAb) and thyroglobulin antibodies were collected. The intensity of thyroiditis and the degree of fibrosis were assessed on pathology.

Results

CAT was evidenced in 19/107 (18%) patients. Of these, 13 (68%) displayed an increased and diffuse ¹⁸FCH thyroid uptake. This uptake pattern was not observed in patients without CAT. SUVmax and SUVmean were higher in patients with CAT than in those without ( P < 0.001). At both acquisition times, SUVmax showed a monotonic relationship with the intensity of thyroiditis (Spearman ρ = 0.44 and 0.51, respectively, P < 0.001) and with the degree of fibrosis (Spearman ρ = 0.55 and 0.62, respectively, P < 0.001). SUVmax showed a linear relationship with TPOAb titers at 20 min (Pearson r = 0.54, P < 0.05; Spearman ρ = 0.59, P = 0.03).

Conclusions

More than two-thirds of the patients with CAT present high and diffuse thyroid ¹⁸FCH uptake. This uptake pattern is highly specific to CAT and is correlated with pathology and TPOAb titers.