Clinical use of 18F-fluoro-ethyl-tyrosine PET co-registered with MRI for diagnostic dilemmas in prolactinoma

Trigt Victoria van; Leontine Bakker; Ling Lu; Iris Pelsma; Marco Verstegen; Furth Wouter van; Lenka Pereira Arias-Bouda; Nienke Biermasz

doi:10.1530/endoabs.99.RC5.1

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Endocrine Abstracts (2024) 99 RC5.1 | DOI: 10.1530/endoabs.99.RC5.1

ECE2024 Rapid Communications Rapid Communications 5: Pituitary and Neuroendocrinology | Part I (8 abstracts)

Clinical use of 18F-fluoro-ethyl-tyrosine PET co-registered with MRI for diagnostic dilemmas in prolactinoma

Victoria van Trigt ¹ , Leontine Bakker ¹ , Ling Lu ² , Iris Pelsma ¹ , Marco Verstegen ³ , Wouter van Furth ³ , Lenka Pereira Arias-Bouda ² & Nienke Biermasz ¹

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¹Leiden University Medical Center, Department of Medicine, Division of Endocrinology, Leiden, Netherlands; ²Leiden University Medical Center, Department of Radiology, Section of Nuclear Medicine, Leiden, Netherlands; ³Leiden University Medical Center, Department of Neurosurgery, Leiden, Netherlands

Purpose : To assess the utility of (¹⁸F)fluoroethyl-L-tyrosine PET co-registered with magnetic resonance imaging (FET-PET/MRI^CR) in patients with difficult-to-localize prolactinoma to inform clinical decision making and treatment planning.

Methods: Retrospective cohort study of 17 consecutive patients with difficult-to-localize prolactinoma undergoing FET-PET/MRICR between October 2020 and Amgust 2022 for either (1) additional information in case of difficult remnants after transsphenoidal surgery (TSS) or pharmacological treatment, or (2) diagnosis in absence of a (clear) adenoma on conventional MRI at diagnosis or after treatment.

Results: FET-PET/MRI^CR identified a lesion in 14/17 patients, yet failed to identify active lesions in 2 patients with negative conventional MRI but prolactin >7.5 times upper limit of normal. FET-PET/MRI^CR results were inconclusive in 1 patient due to diffuse tracer uptake 10 weeks post-surgery. Foci on FET-PET/MRI^CR corresponded completely with the lesion on conventional MRI in 10 patients, partially in 3 patients, and new foci were identified in 4 patients. Functional imaging influenced clinical decision making in 15/17 patients: 7 patients underwent TSS after functional imaging, and 8 patients did not. One patient underwent surgery despite negative FET-PET/MRI^CR due to a high need for alternative treatment, and 1 patient underwent additional diagnostics due to inconclusive FET-PET/MRI^CR results. FET-PET/MRI^CR results were confirmed in all patients undergoing surgery: intraoperatively by identification of adenoma tissue in 5/8 patients, by positive histopathology in 6/8 patients, and by significant decrease in prolactin postoperatively in 7/8 patients. The surgical goal was achieved in 7/8 patients.

Conclusion: FET-PET/MRI^CR can be of added value in the preoperative decision-making process for selected patients with difficult to localize prolactinoma (remnants), or patients lacking a substrate on conventional MRI.