The Diagnostic Accuracy of [18F]Fluorocholine PET/CT for the Preoperative Localization of Hyperfunctioning Parathyroid Glands.

Background/Objectives: The purpose of this study was to compare [18F]Fluorocholine (FCH) PET/CT, ultrasound (US) and dual-phase scintigraphy with [99mTc]Tc-methoxyisobutylisonitrile (MIBI) and [99mTc]Tc-pertechnetate (TcO4-) ([99mTc]Tc-MIBI/[99mTc]TcO4) in the preoperative detection of hyperfunctioning parathyroid glands. Secondary aims were to determine the optimal scanning time of [18F]FCH PET/CT while investigating the correlation between [18F]FCH PET/CT parameters and PTH, calcium levels, lesions size, histopathology, and immunohistochemical analysis. Methods: Patients with primary hyperparathyroidism who underwent US, [99mTc]Tc-MIBI/[99mTc]TcO4 scintigraphy, [18F]FCH PET/CT and parathyroid surgery were retrospectively evaluated. The following PET parameters were calculated: SUVmax and SUVmean, parathyroid retention index (RI) and lesion contrast (LC). Lesions were classified as parathyroid adenomas (PA), hyperplastic parathyroid glands (HP) or parathyroid carcinoma (PC) according to histology. Results: Forty-nine patients were evaluated and 55 lesions were removed at surgery (8 normal glands, 33 PAs, 12 HP glands, 2 PCs). In a lesion-based analysis, the sensitivity and specificity were 68.9% and 28.6% for US, 65.7% and 40.0% for [99mTc]Tc-MIBI/[99mTc]TcO4, 97.8% and 14.3% for early-phase [18F]FCH PET/CT and 95.7% and 12.5% for late-phase [18F]FCH PET/CT. The sensitivity of both early and late [18F]FCH PET/CT acquisitions was statistically higher than that of US and [99mTc]Tc-MIBI/[99mTc]TcO4 scintigraphy. SUVs were statistically higher in PA than in HP, and RI was significantly lower in HP compared with PC, although this difference was based only on two PC cases. Therefore, this result must be considered preliminary and interpreted with caution. Conclusions: [18F]FCH PET/CT performed better than US and [99mTc]Tc-MIBI/[99mTc]TcO4 scan for the detection of hyperfunctioning lesions. The most favorable time point to assess parathyroid lesions appears to be 60 min after injection. However, due to the possible rapid washout of some lesions, a supplementary early acquisition is advisable. SUVmax, SUVmean and RI may predict the histological nature of a parathyroid lesion, but larger studies are needed to confirm these findings.