Endocrine Abstracts

Background

Primary hyperparathyroidism (PHPT) is the third most common endocrine disorder mainly caused by a single parathyroid adenoma. The localization of the parathyroid adenoma is useful for increasing the recovery rate of PHPT, and reducing the complication rate. Conventional localization techniques include neck ultrasound, Tc99m-MIBI-SPECT and CT. However, each one of those has its limitations; particularly in cases of ectopic, or multiple parathyroid adenomas. 11C-methionine PET/CT may be a useful tool for patients who test negative/inconclusive with other techniques.

Aims

To compare sensitivity, specificity of 11C-methionine PET/CT in comparison to conventional imaging techniques.

Materials and methods

We analyzed the data of 59 patients diagnosed with PHPT from 2016 to 2020. All of them underwent ultrasound and a second confirmation test (mainly Tc99m-MIBI-SPECT). In case the result was negative or inconclusive, a third test was administered (mainly CT). In 2019–2020 11C-methionine PET/CT was used as last-line localization technique in 13 patients. All patients underwent parathyroidectomy and pathological findings were used in order to evaluate the characteristics of imaging modalities.

Results

We conducted a single-centre study at the Almazov National Medical Research Centre in order to evaluate the utility of 11C-methionine PET/CT. Sensitivity of PET/CT was 100 %, CT and Tc99m-MIBI-SPECT showed a bit lower sensitivity, at 91% and 84% respectively. The least sensitivity, 71% was ultrasound. The estimated specificities of PET/CT, CT, Tc99m-MIBI-SPECT and ultrasound were 86%, 73%, 79%, 70% respectively. Relatively low specificities of CT and Tc99m-MIBI-SPECT may explain why 37/59 patients required three techniques (ultrasound, CT, Tc99m-MIBI-SPECT). Though 11C-methionine PET/CT was performed in 9/59 as a third-line, and in 4/59 as a forth-line technique, this method showed the highest sensitivity and specificity.

Conclusion

11C-methionine PET/CT demonstrated the highest sensitivity and specificity and may be a valid alternative to conventional imaging in order to elude negative/inconclusive results. In patients with ectopic or multiple lesions, it can help avoiding bilateral cervical exploration, and persistent hyperparathyroidism.