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.
Imaging of tumor biology can be useful for pituitary adenomas (PA). Positron emission tomography (PET) with 11 C-methionine (MET) can reveal aminoacid (AA) uptake and protein synthesis whereas 11 C-raclopride evaluates dopamine D2 receptors (D2) in prolactinomas (PRL), non-functioning PA (NFA) and GH secreting PA (ACR). 18 F-Fallypride (FP) is a molecular tracer of D2. We present 7 patients with PA that were evaluated with PET. Case 1: A 64 year-old male with a PRL (prolactin (PL) of 1477 ng/ml) and a 15X15X18 mm-cystic tumor on MRI. Cabergoline (CB) up to 3.5 mg/week was done, with no changes in tumor size. FP-PET showed low expression of D2 and 11 C-Methionine-PET (MET-PET) showed low AA uptake. Case 2: A 42 year-old male with initial PL levels of 280 ng/ml and a 27x30x30 mm-hemorrhagic PRL on MRI. Treated with CB up to 10 mg/week due to failure to normalize PL. MRI showed a significant reduction in tumor size (9 mm). FP-PET revealed adequate expression of D2 and MET-PET showed moderate AA uptake at the right side of the tumor. Case 3: 27 year-old female, with PL of 470 ng/ml and a 34 mm solid-cystic PRL on MRI. CB was started up to 9 mg/week due to failure to normalize PL, but with a significant reduction of tumor size (6mm). MET-PET did not show uptake, and FP-PET revealed a moderate expression of D2. Case 4: 63 year-old female, diagnosed with a 44x25mm NFA. She had 2 transsphenoidal surgeries (TSS) and posterior radiotherapy, but tumor grew in FU. MET-PET showed high uptake in the PA and FP-PET revealed adequate expression of D2. CB was indicated till 2 mg/week. Case 5: 53 year-old male was diagnosed with ACR with a tumor size of 24x24x30 mm and underwent a TSS. He was treated with octreotide and CB till 3.5 mg/week without IGF-1 normalization. MET-PET revealed mild uptake at site of pituitary tumor, with a higher uptake at its right side. Case 6 and 7: We describe two 59 and 55 year-old females, who were diagnosed with Cushing’s disease (CD), with <6 mm lesions on MRI. MET- PET did not reveal uptake in one of the cases and an upper normal uptake at the pituitary gland in the other. Discussion: PRL with significant tumor reduction showed adequate expression of D2, while the case without changes in size disclosed low expression of D2. The PRL that had D2 expression and significant tumor size reduction did not show uptake with MET, but a decreased uptake has been reported after DA. In NFA we found an adequate expression of D2. Some of those reported to have D2 responded to DA. In ACR, MET-PET was reported to be helpful to identify residual PA and facilitate further treatment. In our case, it showed a localized site of abnormal tracer uptake. In CD, MET-PET was reported to successfully localize microadenomas, but in our cases it failed to identify tumor. In conclusion, metabolic imaging may be a useful tool for PA. It may help in the diagnosis, identify recurrence and monitor response to therapy...
dependiente de adrenocorticotropina (ACTH) es esencial para realizar un tratamiento correcto. La hipersecreción de ACTH es debida en su mayoría a un tumor hipofisario (enfermedad de Cushing) o, en un 10%-20%, a tumores con producción ectópica de esta hormona. Los test no invasivos tienen baja sensibilidad y especificidad para diferenciar estas dos etiologías. El patrón oro lo constituye el cateterismo bilateral de los senos petrosos inferiores (CSP). Mediante el CSP se demuestra la hipersecreción de ACTH a nivel hipofisario al documentar un gradiente de ACTH central a periférico en el drenaje del tumor. Se recomienda realizarlo en todo síndrome de Cushing ACTH dependiente, aunque suele reservarse para pacientes con diagnóstico de hipercortisolismo y hallazgos negativos o equívocos en la resonancia nuclear magnética (RNM) de la región selar.Presentamos el primer caso en Uruguay en que se utilizó el CSP como método diagnóstico, una mujer de 55 años que presentó un hipercortisolismo ACTH-dependiente con una imagen adenohipofisaria <6 mm. El gradiente petroso-periférico confirmó el diagnóstico de enfermedad de Cushing y no hubo complicaciones durante el procedimiento. Posteriormente se realizó la resección del adenoma mediante cirugía transesfenoidal, con buena evolución y confirmación inmunohistoquímica del tumor.
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