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

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.