18F-fluorocholine PET/CT vs. 123I/99mTc-sestaMIBI dual-phase/isotope scintigraphy in primary or secondary hyperparathyroidism.

197 Objectives Compare FCH PET/CT with US and 123I/99mTc-sestaMIBI dual-phase/isotope scintigraphy (MIBI) in patients (pts) with hyperparathyroidism (HPT) and discordant or equivocal results of US and 123I/99mTc-sestamibi dual-phase dual-isotope scintigraphy. Methods 17 pts with 1ry (11), Li induced (1) or 2ry HPT (1 dialysed, 4 grafted) had FCH PET/CT (3MBq/kg). Imaging modalities were evaluated, by on site reading (OSR) and by masked reading (MR), on per-patient and per-lesion bases, with post-surgical histopathology a the standard of truth. Results Equivocal images were first considered as negative. On a per-patient level, the sensitivity Se (at least one abnormal parathyroid gland detected by imaging in its correct site) was for US 38%, for MIBI 69% by OSR and 94% by MR, for FCH PET/CT 88% by OSR and 94% by MR. On a per-lesion level, Se was for US 42%, for MIBI 58% by OSR and 83% by MR, for FCH PET/CT 88% by OSR and 96% by MR. Only one ectopic adenoma was missed by the 3 imaging modalities. Considering equivocal images as positive increased accuracy of OSR of MIBI or of FCH but not of US. FCH PET/CT was significantly superior to US in all approaches, whereas it was more sensitive than MIBI only for OSR considering equivocal images/foci as negative (p=0.04). FCH uptake tended to be more intense in adenomas (Ad) than in hyperplastic parathyroid glands (HPG). Thyroid lesions (suspected in 9 pts) may induce false-positive results as in one oncocytic thyroid adenoma, or false-negative results as in one intrathyroidal Ad. Thyroid cancer (4 cases) was visualised with FCH as with MIBI, with an uptake similar to that of HPG. Conclusions In this pilot study FCH PET/CT was an adequate imaging tool in pts with 2ry as well as1ry HPT, since both Ad and HPG were detected. Furthermore, Se of FCH PET/CT was better than US and was not inferior to dual phase/isotope MIBI scintigraphy. FCH could replace MIBI as the functional agent for HPT imaging but US would still be useful to identify thyroid lesions.