FDG PET/CT Scan and Functional Adrenal Tumors: A Pilot Study for Lateralization

Area of Science:

• Nuclear Medicine
• Endocrinology
• Oncology

Background:

• Bilateral adrenal masses in Cushing's Syndrome (CS) and Conn's Syndrome present diagnostic challenges.
• 18F-FDG uptake by hyperfunctioning adrenal glands is not well-established and could aid in lesion lateralization.

Purpose of the Study:

• To investigate if 18F-FDG PET/CT can identify hyperfunctioning adrenal masses.
• To determine the biological basis for differential 18F-FDG uptake in adrenal masses.

Main Methods:

• 18F-FDG PET/CT scans were performed on patients with nonfunctional adenomas, CS, and Conn's syndrome.
• Maximal standardized uptake values (SUVmax) were measured for adrenal masses.
• Genome-wide expression data and immunohistochemistry were analyzed for GLUT genes.

Main Results:

• Cortisol-secreting masses showed significantly higher SUVmax (5.9) compared to nonfunctioning (4.2) and aldosterone-hypersecreting (3.2) masses (p=0.007).
• A SUVmax cut-off of 5.33 demonstrated 50% sensitivity and 81.8% specificity for cortisol-secreting masses.
• GLUT3 expression was significantly higher in CS masses compared to nonfunctioning and Conn's syndrome masses.

Conclusions:

• 18F-FDG PET/CT exhibits differential uptake patterns across nonfunctioning, aldosterone-hypersecreting, and cortisol-secreting adrenal masses.
• Overexpression of GLUT3 in cortisol-secreting tumors likely drives the observed differential uptake.
• Further research in larger cohorts is needed to confirm 18F-FDG PET/CT's utility in lateralizing cortisol-secreting adrenal masses.