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

The dopamine agonists (DA) have been used widely to treat prolactinomas. However, it is difficult to predict whether the patient will be responsive to DA treatment.We aimed to investigate whether the in vivo expression of DRD2 based on 18F-fallypride PET/MR could predict the therapeutic effect of DA on prolactinomas. Seven patients with prolactinomas completed 18F-fallypride PET/MR. Among them, three patients underwent surgery and further tumor immunohistochemistry. Imaging findings and immunohistochemical staining were compared with treatment outcomes.18F-fallypride PET/MR was visually positive in 7 of 7 patients, and DRD2 target specificity could be confirmed by immunohistochemical staining. A significantly lower tracer standard uptake value (SUV) could be detected in the resistant patients (n = 3) than in the sensitive patients (n = 4; SUVmean, 4.67 ± 1.32 vs. 13.57 ± 2.42, p < 0.05). DRD2 expression determined by 18F-fallypride PET/MR corresponded with the DA treatment response.18F-fallypride PET/MR may be a promising technique for predicting DA response in patients with prolactinoma.