Incidental Pituitary FDG Uptake on PET-CT: A Retrospective Review of Current Practice and Outcomes at a UK Tertiary...

Fluorine-18 fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET-CT) is widely used in malignancy diagnosis and surveillance. However, benign conditions also increase avidity. Distinguishing between benign and pathological uptake is critical. Rising PET-CT utilisation has led to increased detection of incidental pituitary FDG uptake. Referral pathways and secondary imaging remain inconsistent, and no UK guidelines exist. This study aims to review our current practice and assess the potential role of SUVmax to differentiate physiological from pathological uptake in the pituitary gland.

A retrospective single-centre cohort study was conducted at a UK tertiary hospital.

Among 15824 PET-CT scans between 01/01/2017-30/06/2024, 70 patients (mean age 72.1 ± 1.3 years, 25.7% female) were included.

Demographics, primary pathology, oncological treatment, SUVmax on initial PET-CT, secondary imaging findings, endocrine referral, and pituitary biochemistry were collected.

48 patients (68.6%) underwent secondary imaging; 70.8% (n = 34) were normal. Pathological findings included macroadenomas (n = 6), microadenomas (n = 3), and other lesions (n = 5). Mean SUVmax was significantly higher in patients with pituitary pathology (pituitary adenomas- 20.62 ± 4.82; all pathology- 16.74 ± 3.80) versus normal imaging- 4.66 ± 0.26 (p < 0.001). A SUVmax threshold of 4.75 yielded 100% sensitivity and 53.9% specificity for detecting pituitary pathology (ROC curve; 95% CI: 69%-100%).

Our review highlights significant variation in referral patterns for secondary imaging and to the Endocrine department. We suggest potential use of SUVmax threshold to distinguish physiological from pathological pituitary FDG uptake. Further validation in larger cohorts is warranted before routine clinical application.