Utility of suvmax threshold for pathological discrimination of incidental fdg-pet pituitary uptake - a united kingdom single centre retrospective analysis

Trevor Tam; Phyu Naing Thin Kyi; Lee Elzubeir; Ramona-Rita Barbara; Rupa Ahluwalia

doi:10.1530/endoabs.109.P202

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Endocrine Abstracts (2025) 109 P202 | DOI: 10.1530/endoabs.109.P202

SFEBES2025 Poster Presentations Neuroendocrinology and Pituitary (48 abstracts)

Utility of suvmax threshold for pathological discrimination of incidental fdg-pet pituitary uptake - a united kingdom single centre retrospective analysis

Trevor Tam ^1,2 , Thin Kyi Phyu Naing ³ , Lee Elzubeir ¹ , Ramona-Rita Barbara ¹ & Rupa Ahluwalia ¹

Author affiliations

¹Norfolk and Norwich University Hospital, Norwich, United Kingdom; ²University of East Anglia, Norwich, United Kingdom; ³Cambridge University Hospitals, Cambridge, United Kingdom

Background: Positron emission tomography-computed tomography (PET-CT) is essential for cancer staging. Fluorine-18 fluorodeoxyglucose (FDG), marks increased cellular activity as maximum Standardised Uptake Value (SUVmax). Malignancies show elevated FDG uptake, benign conditions (inflammation, benign tumours, post-treatment) also increase avidity. Distinguishing between benign and pathological uptake is critical. Currently there are no UK guidelines for evaluating incidental pituitary uptake on FDG-PET CT scans.

Methods: Retrospective analysis of PET-CT scans at a UK single centre. 88 patients with ‘pituitary’ mentioned in scan report (January 2017-June 2024) were identified. 20 patients excluded (5- known pituitary tumours, 5- pending investigations, 9- other centre, 1- deceased).

Results: 68 patients (mean age 71.6 years; median age 70.5 ± 13.5 years) (25% females). Secondary imaging- performed in 48/68 patients: (23- MRI Pituitary, 21- CT Head, 3- MRI Head, 1-CT Pituitary) Mean uptake in pituitary incidentaloma: 20.620 ± 4.819 (range: 4.8 - 57.2), median 31.0 ± 26.2. Mean uptake in all cases of positive secondary imaging (pituitary adenoma + other pathologies including malignancy): 16.743 ± 3.799, median 31.0 ± 26.2 (range: 4.8 - 57.2). Mean uptake in normal secondary imaging: 4.659 ± 0.262 (range: 2.9 - 9.1), median 6.0 ± 3.1. Significant difference in SUVmax value (P < 0.001) between pituitary incidentaloma vs normal imaging, and in all pathology on secondary imaging vs normal imaging.

Primary malignant condition:
Condition	Patients
Dermatological	n =19 (27.9%)
Respiratory	n =9 (13.2%)
Otolaryngological	n =4 (5.9%)
Urological	n =1 (1.5%)
Endocrine	n =1 (1.5%)
Non-malignant disease	n =8 (11.8%)
Haematological	n =26 (38.2%)

Secondary imaging results
Results	Patients
Pituitary macroadenoma	n =6 (12.5%)
Pituitary microadenoma	n =3 (6.3%)
Metastatic disease	n =1 (2.1%)
Neurological spread from primary malignancy	n =1 (2.1%)
Indeterminate nodule	n =1 (2.1%)
Osmotic demyelination syndrome	n =1 (2.1%)
Pituitary macroadenoma + metastatic disease	n =1 (2.1%)
Normal	n =34 (70.8%)

Conclusion: We propose that a cut-off SUVmax value of 4.75 (100% sensitive, 61.8% specific) could be used to differentiate between physiological versus non-physiological uptake in the pituitary fossa.