18F-fluorocholine PET/CT is more sensitive than 11C-methionine PET/CT for the localization of hyperfunctioning parathyroid tissue in primary hyperparathyroidism.

Purpose: Preoperative molecular imaging is paramount to direct surgery in primary hyperparathyroidism (pHTP). We investigate the diagnostic performance of 18F-fluorocholine (18F-FCH) PET/CT compared to 11C-methionine (11C-MET) PET/CT for the localization of hyperfunctioning parathyroid tissue in patients with pHTP and negative or inconclusive 99mTc-sestaMIBI SPECT (MIBI) findings. Materials and Methods: Fifty-eight patients with biochemical evidence of pHTP and negative or inconclusive MIBI were referred for pre-surgical detection and localization of hyperfunctioning parathyroid tissue by 11C-MET- and 18F-FCH-PET/CT. The PET/CT results were classified into 3 categories (positive, inconclusive or negative) based on the nodular aspect of tracer uptake and the visualisation of corresponding nodules on CT. The PET/CT results were correlated with the surgical and histopathological findings used as gold standard. Results: Fifty-three patients were included for analysis. 18F-FCH-PET/CT was positive in 39 patients (74%), inconclusive in 5 (9%) and negative in 9 (17%), compared to 25 (47%), 12 (23%) and 16 (30%) respectively for 11C-MET-PET/CT. 18F-FCH localized 11 additional foci (6 positive and 5 inconclusive) compared to 11C-MET. Twenty-six patients (sex F/M ratio16/10) underwent surgery with resection of 31 lesions (22 adenomas, 6 hyperplastic glands, 3 carcinomas) and 1 normal gland. At follow-up, twenty-one (81%) patients were considered cured after surgery, while 3 (12%) patients had persistence of hypercalcaemia. With inconclusive cases being considered as negative, 18F-FCH-PET/CT correctly localized 26 lesions in 24/26 (92%) patients compared to 16 lesions in 15/26 (58%) patients localized by 11C-MET-PET/CT. Per patient-based sensitivity and positive predictive value (PPV) were 96% and 96% for 18F-FCH and 60% and 94% for 11C-MET (p<0.0001). Per lesion-based sensitivity and PPV were respectively 84% and 90% for 18F-FCH vs. 52% and 94% for 11C-MET (p