¹⁸F-fluoro-ethyl-tyrosine PET co-registered with MRI in patients with persisting acromegaly

To report our experience with ¹⁸F-fluoro-ethyl-tyrosine (FET) positron emission tomography-computed tomography (PET-CT) co-registered with magnetic resonance imaging (MRI) (FET-PET/MRI^CR) in the care trajectory for persistent acromegaly.

Prospective case series.

Ten patients with insufficiently controlled acromegaly referred to our team to evaluate surgical options.

FET-PET/MRICR was used to support decision-making if MRI alone and multidisciplinary team evaluation did not provide sufficient clarity to proceed to surgery.

FET-PET/MRI^CR showed suspicious (para)sellar tracer uptake in all patients. In five patients FET-PET/MRI^CR was fully concordant with conventional MRI, and in one patient partially concordant. FET-PET/MRI^CR identified suggestive new foci in four other patients. Surgical re-exploration was performed in nine patients (aimed at total resection (6), debulking (2), diagnosis (1)), and one patient underwent radiation therapy. In 7 of 9 (78%) operated patients FET-PET/MRI^CR findings were confirmed intraoperatively, and in six (67%) also histologically. IGF-1 decreased significantly in eight patients (89%). All patients showed clinical improvement. Complete biochemical remission was achieved in three patients (50% of procedures in which total resection was anticipated feasible). Biochemistry improved in five and was unchanged in one patient. No permanent complications occurred. At six months, optimal outcome (preoperative intended goal achieved without permanent complications) was achieved in six (67%) patients and an intermediate outcome (goal not achieved, but no complications) in the other three patients.

In patients with persisting acromegaly without a clear surgical target on MRI, FET-PET/MRI^CR is a new tracer to provide additional information to aid decision-making by the multidisciplinary pituitary team.