18F-fallypride and 11C-methionine positron emission tomography/computed tomography for the study of prolactinomas and nonfunctioning pituitary adenomas: A case series

Abstract

Some studies have assessed the expression of dopaminergic dopamine 2 (D2)/3 receptors in prolactinomas and nonfunctioning pituitary adenomas (NFPA) by positron emission tomography/computed tomography (PET/CT) with 11 C-raclopride, proving that this modality can be useful to predict the response to treatment with dopamine agonists. However, the use of 11 C-labeled radiotracers is limited, as it requires a cyclotron in the PET center. 18 F-fallypride is a radiotracer that has proven useful in assessing the expression of D2/3 receptors. As it is labeled with 18 F, it can be produced and transported to distant PET centers. There are no studies on the usefulness of 18 F-fallypride for the evaluation of patients with prolactinomas and NFPA. The aim of this study was to describe the first case series of patients with prolactinomas and NFPA studied with 18 F-fallypride and 11 C-methionine PET/CT to reveal D2/3 expression and amino acid (AA) metabolism. 18 F-fallypride and 11 C-methionine uptake were assessed in a case series of six patients, five with prolactinomas and one with a NFPA, and compared with clinical presentation and follow-up at 6–18 months. All patients presented with macroadenomas, with a wide range of AA metabolism, as revealed by 11 C-methionine PET/CT. 18 F-fallypride PET/CT identified low to moderate/high D2/3 expression in the tumors. The patient that presented low expression of D2/3 in the tumor and high AA metabolism showed a poor response to DA therapy. 18 F-fallypride was able to reveal D2/3 receptor expression in prolactinomas and NFPA, with the advantage of been a more accessible radiotracer in comparison with previous 11 C labeled analogs.

Novel imaging techniques in refractory pituitary adenomas

“…Finally, we have discussed four clinical scenarios in which molecular imaging can significantly augment the effectiveness and timeliness of decision-making by accurately localizing sites of disease activity. responsiveness of prolactinomas and non-functioning pituitary adenomas to dopamine agonists, thereby facilitating more timely identification of tumors that are likely to be refractory to medical therapy, and allowing other treatment modalities to be considered at an earlier stage [12,13]. Peptide Receptor Radionuclide Therapy (PRRT), typically delivered using radiolabeled somatostatin receptor ligands (e.g.…”

DRD2 expression based on 18F-fallypride PET/MR predicts the dopamine agonist resistance of prolactinomas: a pilot study

“…Nuclear medicine methods are clinically validated and have been increasingly integrated into the management of pituitary adenomas [21]. Recently, Damian et al described that 18 F-fallypride PET/CT coregistered with MRI was used to reveal the expression of DRD2 in prolactinomas and nonfunctioning adenomas [15]. Compared to sequentially acquired PET and MRI, integrated PET/MR systems provide more accurate images, shorten acquisition time, and reduce motion artifacts [22].…”

“…However, dopaminergic imaging has rarely been studied in prolactinomas. Only 11 C-N-methylspiperone, 11 Craclopride, 18 F-FDOPA and 18 F-fallypride as PET tracers have been used in prolactinomas [13][14][15]. Due to its convenience and stability, 18 F-fallypride has recently been successfully tested as a PET tracer to study prolactinomas [15].…”

“…Only 11 C-N-methylspiperone, 11 Craclopride, 18 F-FDOPA and 18 F-fallypride as PET tracers have been used in prolactinomas [13][14][15]. Due to its convenience and stability, 18 F-fallypride has recently been successfully tested as a PET tracer to study prolactinomas [15]. However, this study was performed using PET/CT which can not show the detailed anatomical characteristics when compared with PET/MR.…”

Recent advances in understanding and managing pituitary adenomas

“…68 Ga CRH PET-CT localized a corticotropinoma in 24 cases of CD, including 10 cases with small adenomas smaller than 6 mm (four cases were negative on MRI) 26 . Finally, 18 F-fallypride may identify dopamine 2/3 receptor expression in prolactinomas and non-functioning PAs 27 .…”