Clinical value and limitations of [¹¹C]-methionine PET for detection and localization of suspected parathyroid adenomas

Purpose: The aim of this study was to assess the clinical value of [¹¹C]methionine-PET (MET-PET) for detection and localization of parathyroid adenomas in patients without prior thyroidectomy. Methods: A retrospective analysis of patients with suspected parathyroid adenomas undergoing imaging with MET-PET was performed. Prior thyroidectomy was an exclusion criterion. Forty-one patients with a total of 49 MET-PET scans were included. MET-PET consisted of whole-body images obtained 15-20 min after injection of 430±81 MBq of MET using a dedicated PET scanner. Imaging findings were validated by histology or other imaging studies and clinical follow-up on a lesion, side, and location basis. Comparison of PET results to other imaging modalities including ultrasound, MIBI scintigraphy, and morphological imaging [computed tomography (CT) and/or magnetic resonance imaging] and subgroup analysis of primary vs. secondary hyperparathyroidism was performed. Results: Twenty-three of 49 PET scans revealed pathologic findings, whereas 26 of 49 scans were negative. Validation of PET findings for detection and localization of parathyroid adenomas resulted in an overall sensitivity of MET-PET of 54%, 49%, and 35% on a lesion, side, and location basis, respectively. Sensitivity of MET-PET was inferior compared to ultrasonography (50% vs. 93%), MIBI scintigraphy (53% vs. 74%) and morphological imaging (52% vs. 74%). Subgroup analysis revealed higher sensitivity for MET-PET in secondary HPT (sHPT) than primary HPT (pHPT; 62% vs. 43%; side basis). Conclusions: In patients with initial diagnosis of hyperparathyroidism and no prior thyroidectomy, the sensitivity of MET-PET for detection and localization of parathyroid adenomas is markedly lower compared to previous reports. While performance was better in sHPT, we believe that MET-PET cannot be recommended for pHPT localization in this clinically relevant subcollective. The clinical value of MET/PET in patients with hyperparathyroidism should be further investigated in a prospective study utilizing anatometabolic imaging with a PET/CT device.