Cushing's disease results from adrenocorticotropic hormone (ACTH) secretion by corticotroph pituitary neuroendocrine tumors (PitNETs). Magnetic resonance imaging (MRI) is the reference modality for etiological diagnosis but may to visualize small corticotroph microadenomas in up to 30% of the cases, and false positives may occur.
The study hypothesis is that positron emission tomography (PET) using \[18F\]fluoroethyl-L-tyrosine (\[18F\]FET) improves localization of ACTH-secreting corticotroph microadenomas compared with MRI and could inform surgical planning and reduce reliance on invasive inferior petrosal sinus sampling.
This observational cohort (retrospective and prospective data) will assess the diagnostic performance of \[18F\]FET PET for tumor localization using postoperative histopathology as the gold standard.
Secondary aims include:
1. assessing cases in which PET modifies localization relative to MRI and is correct by gold standard; 2. inter-reader agreement between two nuclear medicine physicians; 3. correlations between PET signal and biochemical markers of hypercortisolism 4. uni- and multivariable analyses of clinical and imaging parameters influencing PET results; 5. association between PET findings and subsequent biological remission.
Adults (≥18 years).
Biochemical diagnosis of Cushing's disease as part of initial management.
Pituitary MRI performed; if visible, microadenoma <10 mm in diameter.
Indication for discussion in multidisciplinary tumor board for surgical management.
Minor (age <18 years).
Macroadenoma of the pituitary.
ACTH-dependent hypercortisolism secondary to ectopic secretion.
Adults treated at a tertiary academic hospital with biochemically confirmed Cushing's disease, evaluated by pituitary MRI and \[18F\]FET PET as part of diagnostic work-up, and discussed for surgery.
Cohort
Cross-sectional
Data-only evaluation of [18F]FET PET, pituitary MRI, and biomarkers
Other interventionNo study-specific procedures. The study evaluates existing \[18F\]FET PET imaging pituitary MRI, and routine biochemical markers collected as part of standard care.
[18F]FET PET Performance for Localizing Corticotroph Pituitary Adenomas
Proportion (%) of correct localization of the adenoma by \[18F\]FET PET, using postoperative histopathological examination of the surgical specimen as the reference standard.
Effect of PET on Tumor Localization Versus MRI
Among cases in which the PET-suggested localization differs from MRI, the proportion (%) in which PET correctly localizes the adenoma (per the primary endpoint definition).
Inter-Reader Agreement of [18F]FET PET Interpretation
Proportion (%) agreement between the two nuclear medicine physicians' PET interpretations (inter-reader agreement).
Correlation Between PET SUV and Hypercortisolism Biomarkers
Correlation between \[18F\]FET PET and biochemical markers
Determinants of PET Performance (Clinical/Biological/Imaging)
Univariable and multivariable analyses of variables that may influence PET results.
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