ECE2020 Audio ePoster Presentations Pituitary and Neuroendocrinology (217 abstracts)
Gallium-68 -DOTATATE PET imaging in clinically non-functioning pituitary macroadenomas
Tessel M. Boertien 1 , Jan Booij 2 , Charles BLM Majoie 3 , ML Drent 4 , Alberto M Pereira 5 , Nienke Biermasz 5 , Suat Simsek 4,6 , Ronald Groote Veldman 7 , Marcel PM Stokkel 8 , Peter H. Bisschop 1 & Eric Fliers 1
1Amsterdam UMC, University of Amsterdam, Department of Endocrinology and Metabolism, Amsterdam, Netherlands; 2Amsterdam UMC, University of Amsterdam, Radiology and Nuclear Medicine, Amsterdam, Netherlands; 3Amsterdam UMC, University of Amsterdam, Department of Radiology and Nuclear Medicine, Amsterdam, Netherlands; 4Amsterdam UMC, VU University, Department of Internal Medicine, Section of Endocrinology, Amsterdam, Netherlands; 5Leiden University Medical Center (LUMC), Department of Medicine, Division of Endocrinology, and Center for Endocrine Tumors Leiden (CETL), Leiden, Netherlands; 6Northwest Clinics (NWZG), Department of Internal Medicine, Alkmaar, Netherlands; 7Medisch Spectrum Twente (MST), Department of Internal Medicine, Enschede, Netherlands; 8Netherlands Cancer Institute (NKI), Department of Nuclear Medicine, Amsterdam, Netherlands
Background: Clinically non-functioning pituitary macroadenomas (NFMA) have been reported to express various somatostatin receptor (SSTR) subtypes, but results are inconsistent across different studies. This may be related to limited sensitivity and specificity of techniques used to date, i.e. immunohistochemistry in surgical specimens and 111In-DTPA-octreotide scintigraphy (Octreoscan) in vivo. The aim of this study was to assess SSTR expression in NFMA in vivo using 68Ga-DOTATATE PET, which provides superb SSTR2affinity and offers superior sensitivity and spatial resolution as compared to Octreoscan. An additional interest was the proportion of patients with a T2-hypointense adenoma on MRI and the relation with tracer uptake, as T2-hypointensity has been associated with higher SSTR2expression in GH-secreting adenomas.
Methods: Forty-nine patients diagnosed with NFMA underwent 68Ga-DOTATATE PET/CT of the head in the framework of a randomised controlled trial assessing the effect of the somatostatin analogue lanreotide on NFMA size. 68Ga-DOTATATE uptake was assessed after co-registration with T1-weighted pituitary MRI. A circular region of interest was placed within the adenoma and the mean standard uptake value (SUVmean) was evaluated. An SUVmean of >2 was considered positive. Signal intensity of the adenoma was assessed visually on a coronal T2-weighted sequence of the same MRI and was classified as hypointense, isointense or hyperintense as compared to normal pituitary tissue.
Results: 68Ga-DOTATATE uptake was positive in 45/49 patients (92%), with SUVmean in positive adenomas ranging from 2.1 to 14.4 (median 5.5). A T2-hypointense, -isointense, and -hyperintense adenoma was observed in 2 (4%), 13 (37%), and 33 (69%) patients, respectively. In one patient T2-signal intensity was not assessed due to a predominant cystic adenoma. SUVmean was not associated with maximum NFMA size or with T2-hypointensity.
Conclusions: This first series of 68Ga-DOTATATE PET performed in NFMA patients demonstrates in vivo SSTR expression in the vast majority of cases. The high positive uptake rate when compared to earlier results obtained using Octreoscan (92% vs ~66%) most probably reflects the superior sensitivity and higher spatial resolution of PET imaging. Only 2 patients had a T2-hypointense adenoma, which did not coincide with high tracer uptake. It thus remains uncertain whether T2-hypointensity reflects SSTR2 expression. The clinical use of 68Ga-DOTATATE PET in selecting NFMA patients for somatostatin analogue treatment should be evaluated in well-designed intervention trials.
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Endocrine Abstracts
ISSN 1470-3947 (print) | ISSN 1479-6848 (online)
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