Head-to-head comparison of [C]methionine PET, [C]choline PET, and 4-dimensional CT as second-line scans for detection of parathyroid adenomas in primary hyperparathyroidism.

Purpose: Accurate preoperative localization is imperative to guide surgery in primary hyperparathyroidism (pHPT). It remains unclear which second-line imaging technique is most effective after negative first-line imaging. In this study, we compare the diagnostic effectiveness of [C]methionine PET/CT, [C]choline PET/CT, and four dimensional (4D)-CT head-to-head in patients with pHPT, to explore which of these imaging techniques to use as a second-line scan.

Methods: We conducted a powered, prospective, blinded cohort study in patients with biochemically proven pHPT and prior negative or discordant first-line imaging consisting of ultrasonography and Tc-sestamibi. All patients underwent [C]methionine PET/CT, [C]choline PET/CT, and 4D-CT. At first, all scans were interpreted by a nuclear medicine physician, and a radiologist who were blinded from patient data and all imaging results. Next, a non-blinded scan reading was performed. The scan results were correlated with surgical and histopathological findings. Serum calcium values at least 6 months after surgery were used as gold standard for curation of HPT.

Results: A total of 32 patients were included in the study. With blinded evaluation, [C]choline PET/CT was positive in 28 patients (88%), [C]methionine PET/CT in 23 (72%), and 4D-CT in 15 patients (47%), respectively. In total, 30 patients have undergone surgery and 32 parathyroid lesions were histologically confirmed as parathyroid adenomas. Based on the blinded evaluation, lesion-based sensitivity of [C]choline PET/CT, [C]methionine PET/CT, and 4D-CT was respectively 85%, 67%, and 39%. The sensitivity of [C]choline PET/CT differed significantly from that of [C]methionine PET/CT and 4D-CT (p = 0.031 and p < 0.0005, respectively).

Conclusion: In the setting of pHPT with negative first-line imaging, [C]choline PET/CT is superior to [C]methionine PET/CT and 4D-CT in localizing parathyroid adenomas, allowing correct localization in 85% of adenomas. Further studies are needed to determine cost-benefit and efficacy of these scans, including the timing of these scans as first- or second-line imaging techniques.