The Significance of 18F-Fluorocholine-PET/CT as Localizing Imaging Technique in Patients with Primary Hyperparathyroidism and Negative Conventional Imaging.

Objective: The essential prerequisite for focused parathyroidectomy in patients with primary hyperparathyroidism (pHPT) is proper localization of all autonomic tissue. Sensitivity of conventional imaging modalities (ultrasound, 99m Tc-sestamibi scintigraphy/SPECT/CT) is influenced by different factors (i.e., size/weight and position of autonomic tissue) and decreases in the presence of a multinodular goiter. Therefore, a considerable percentage of pHPT patients have negative or equivocal localization studies before surgery. The aim of this study is to evaluate the utility of FCH-PET/CT for preoperative localization in patients with pHPT and negative/equivocal 99m Tc-sestamibi scintigraphy/SPECT/CT and/or ultrasound.

Methods and measurements: Between 2014 and 2017, a total of 39 patients with pHPT and negative/equivocal conventional imaging were referred for FCH-PET/CT. In the analysis, we included those ( n  = 23) who had surgery and a histopathologic workup of the lesions.

Results: 19 of 23 patients demonstrated no tracer uptake with 99m Tc-sestamibi scintigraphy/SPECT/CT, 6 patients had an equivocal sonographic lesion, and multinodular goiter was present in 43% (10/23). In 21 of 23 patients, hyperfunctioning parathyroid tissue was identified correctly by FCH-PET/CT [21 true positive, 1 false negative, and 1 false positive; per-patient sensitivity 95.5% (95% confidence interval {CI}, 77.2-99.9)]. 29 lesions were resected [21 true positives, 3 false negatives, 1 false positive, and 4 true negatives; per-lesion sensitivity 87.5% (95% CI, 67.6-97.3)]. All patients were classified as having surgical success according to a decrease of intraoperative parathyroid hormone of ≥50% and normalization of postoperative serum calcium levels.

Conclusion: Despite a high prevalence of multinodular goiter, diagnostic accuracy of FCH-PET/CT in our patient group was excellent. Therefore, FCH-PET/CT is a promising new imaging tool in patients with pHPT and negative/equivocal results by conventional imaging techniques.