Additional value of integrated 18F-choline PET/4D contrast-enhanced CT in the localization of hyperfunctioning parathyroid glands and correlation with molecular profile.

PURPOSE: The localization of hyperfunctioning parathyroid gland(s) (HPTG) in patients with primary hyperparathyroidism (PHPT) with negative or inconclusive first-line imaging is a significant challenge. This study aimed to evaluate the role of integrated 18F-choline PET/4D contrast-enhanced computed tomography (4DCeCT) in these patients, compare its detection rate and sensitivity with those of 18F-choline PET/CT and (4DCeCT), and analyse the association between choline metabolism and morphological, biochemical and molecular parameters of HPTG. METHODS: We prospectively enrolled 44 PHPT patients with negative or inconclusive first-line imaging. 18F-Choline PET/CT and 4DCeCT were performed at the same time, and integrated 18F-choline PET/4DCeCT images were obtained after coregistration. Experienced physicians examined the images. The SUVratio and degree of contrast enhancement were recorded for each positive finding. Histopathology, laboratory and multidisciplinary follow-up were used as the standard of reference. Both the detection rates and sensitivities of the three imaging modalities were calculated retrospectively. Immunohistochemistry was performed to evaluate the molecular profile of HPTGs. RESULTS: 18F-Choline PET/4DCeCT was positive in 32 of 44 patients with PHPT (detection rate 72.7%), and 31 of 31 surgically treated patients (sensitivity 100%). These results were significantly (p < 0.05) better than those of 18F-choline PET/CT (56.8% and 80%, respectively) and those of 4DCeCT (54.5 and 74%, respectively). A significant correlation between SUV and calcium level was found. In a multivariate analysis, only calcium level was significantly associated with 18F-choline PET/4DCeCT findings. SUVratio and Ki67 expression were significantly correlated. CONCLUSION: Integrated 18F-choline PET/4DCeCT should be considered as an effective tool to detect PHPT in patients with negative or inconclusive first-line imaging. Choline metabolism is correlated with both calcium level and Ki67 expression in HPTG.

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 18F-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 131I 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 18F-FDG PET/CT (PET+/131I+), 2. radioiodine refractory with positive 18F-FDG PET/CT (PET+/131I-) and 3. radioiodine avid with negative 18F-FDG PET/CT (PET-/131I+). MeanSUV of FDG-avid lesions was assessed and averaged for 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+/131I+, PET+/131I- and PET-/131I+ 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+/131I+ 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 18F-FDG PET/CT further testify the role of TgAb as surrogate tumor marker in DTC.