Endocrine Abstracts

Background: Detection of MRI-negative ACTH-producing pituitary adenomas is a challenge in the management of patients with Cushing’s disease. There are some data on the possibility of pituitary adenomas to accumulate 18F-fluorodeoxyglucose (18F-FDG) during the 18F-FDG positron emission tomography and computer tomography (18F-FDG PET/CT).

Aim: To study the potential of brain 18F-fluorodeoxyglucose PET/CT for localization of MRI-negative ACTH-producing pituitary adenomas.

Materials and methods: Twenty one patients were enrolled. 16 patients had Cushing’s disease (three men and thirteen women), among them seven had newly diagnosed disease and nine had persistence or recurrence of hypercortisolism after the previous transsphenoidal adenomectomy (TSS). MRI scans were negative in patients with newly diagnosed disease and uncertain (postoperative changes-8 patients; secondary ‘empty sella’-1 patient) in patients after TSS. In all patients pituitary source of ACTH hyperproduction was confirmed by bilateral cavernous and inferior petrosal sinuses sampling. Five patients had neuroendocrine tumors (NETs) with ACTH-ectopic production (pheochromocytoma-1; thymus NET -1; lung NET – 3: among them two patients previously had underwent bilateral adrenalectomy due to severe hypercortisolism and failure to find the source of ACTH-ectopy). Brain 18F-fluorodeoxyglucose PET/CT was performed in all patients (in patients with suspected NET it was a part of total body 18F-FDG PET/CT).

Results: Among sixteen Cushing’s disease patients fifteen had had focal increased 18F-FDG uptake on pituitary PET/CT scans. All this patients had undergone TSS. In eleven cases diagnosis of ACTH-producing pituitary adenoma was confirmed by pathology examination, among them in seven cases the remission of hypercortisolism was achieved. In four patients the result of pathology examination was negative, but all of them developed remission of hypercortisolism after the TSS. One patient had had negative18F-FDG uptake on PET/CT scans, he was re-examined and the remission of hypercortisolism was diagnosed. All patients with NETs, including those who had previously undergone bilateral adrenalectomy showed negative 18F-FDG uptake on pituitary PET/CT scans.

Conclusion: According to our study brain 18F-fluorodeoxyglucose PET/CT may be useful for localization of MRI-negative ACTH-producing pituitary adenomas, but further research is necessary for the confirmation of these data.