18F-FDG PET rarely provides additional information to 11C-methionine PET imaging in hyperparathyroidism

AIM: The aim of this study was to assess the utility of combined C-methionine and ¹⁸F-FDG PET/CT imaging in hyperparathyroidism. PATIENTS AND METHODS: We reviewed all scans performed for hyperparathyroidism with both C-methionine and ¹⁸F-FDG PET/CT or PET in our institution since 1993. Forty-three patients (47 pairs of scans) were included (13 men and 30 women) with a mean age of 63 years. ¹¹C-methionine and F-FDG PET/CT scans were classified as positive or negative for localization of abnormal parathyroid tissue, and the site of uptake was noted in the positive scans. Other concurrent imaging (^99mTc-MIBI scintigraphy, ultrasonography, CT, or MRI) findings were also noted when performed. Clinical follow-up information was available in 27 patients (30 episodes). RESULTS: Of the 47 PET scan episodes, 23 (49%) were positive. Twenty-two C-methionine scans showed abnormal focal localization of which 10 also showed concordant abnormal F-FDG uptake. One patient was positive with ¹⁸F-FDG and negative with ¹¹C-methionine.Of the 16 patients who underwent subsequent surgery, 6 had concordant C-methionine, ¹⁸F-FDG, and surgical findings; 6 had concordant C-methionine and surgical findings; 1 had concordant F-FDG and surgical findings; and 3 had both PET scans negative but had adenomas excised during surgery.Of the 3 with both PET scans negative and discordant surgical findings, 1 had mediastinal parathyroid lipoadenoma excised and 2 had normally sited parathyroid adenoma excised. CONCLUSIONS: ¹⁸F-FDG PET/CT rarely provides additional information and could be saved for patients in whom ¹¹C-methionine PET/CT is negative.