Endocrine Abstracts

Background : Parathyroid tumors are considered to be parathyroid neuroendocrine neoplasia (NEN), according to the recent IARC-WHO classification updates. Primary hyperparathyroidism (PHPT) develops commonly in patients with multiple neuroendocrine neoplasia syndromes (MEN), when it occurs along with pituitary, gastro-entero-pancreatic or other NENs. The latter requires total-body 68Ga-DOTA-peptides PET/CT. Its major advantage is to detect additional tumors with other localizations, particularly if CT is performed with contrast enhancement. Therefore, simultaneously this technique may reveal parathyroid NENs.

Aims: To determine Ga68-DOTA-peptide PET/CT utilities in parathyroid NENs diagnostics in PHPT patients.

Materials and methods : Sixteen patients with PHPT were included in the study, 11 patients were newly diagnosed, 5 patients had PHPT recurrence. 13 patients were tested for MEN1 mutation, and 7 harbored it. Parathyroid adenomas were localized with neck ultrasound, Tc99m-sestamibi parathyroid scintigraphy or SPECT/CT, CT, PET/CT with 11C-methionine or 11C-choline. Ga68-DOTA-peptide PET/CT was performed in all patients: Ga68-DOTA-TATE PET/CT in 14 patients and Ga68-DOTA-NOC PET/CT – in 2 patients. Parathyroidectomy (PTX) was performed in 10 patients.

Results: 16 patients had 27 parathyroid adenomas; 23/27 were found by conventional imaging and 4/27 – through bilateral cervical exploration. Among operated patients (n=10) pathology examination revealed 17 parathyroid adenomas, while 6 patients were not operated on due to various reasons. Eight patients harbored single adenomas, five patients – double adenomas, three patients – triple adenomas. Ga68-DOTA-peptide high uptake was found in 18/27 lesions and all of them appeared to be parathyroid adenomas; 12/18 adenomas were verified by the histological examination, the remaining 6/18 – by the conventional imaging since they did not undergo PTX. In five patients 9/27 parathyroid adenomas did not show Ga68-DOTA-peptide uptake and were found by other imaging techniques (5/9) or during PTX (4/9). All these five patients had MEN1 syndrome. Thus, among 27 parathyroid adenomas PET/CT with Ga68-DOTA-peptide revealed 18 lesions, and the sensitivity of the method was 67%. All focuses of Ga68-DOTA-peptide uptake corresponded to parathyroid NENs, hence the specificity was 100%. Therefore parathyroid adenomas’ ability to accumulate Ga68-DOTA-peptides during PET/CT is not an exclusive property of MEN1-assosiated parathyroid NENs.

Conclusion: Incidentally localized focuses of high Ga68-DOTA-peptides uptake on PET/CT in the parathyroid glands’ allocation may be a reason to exclude PHPT. In case the diagnosis is confirmed, additional conventional imaging may be avoided and patient may be referred directly to PTX, particularly, if PET/CT is performed with contrast enhancement and other PET-negative lesions suspected for parathyroid NENs are not found.