FDG PET/CT Scan and Functional Adrenal Tumors: A Pilot Study for Lateralization.
BACKGROUND
Patients with Cushing's Syndrome (CS) and Conn's Syndrome with bilateral adrenal masses pose a dilemma. Uptake of 18F-FDG by hyperfunctioning adrenal glands has not been previously reported and may help lateralize. The aim was to determine if 18F-FDG PET/CT scan could identify hyperfunctioning adrenal masses and determine a biological basis for uptake.


METHODS
Patients with nonfunctional adenomas (n = 9), CS (n = 11), and Conn's syndrome (n = 4) underwent an 18F-FDG PET/CT scan with a volume of interest circumscribing each mass to obtain a maximal standardized uptake value (SUVmax). Thirty-two adrenal masses were analyzed. Genome-wide expression data from an independent cohort were analyzed in nonfunctioning adenomas (n = 20), Conn's syndrome (n = 29), and CS (n = 24) focusing on GLUT genes. For genes differentially expressed, immunohistochemistry was performed on tissue samples.


RESULTS
Cortisol-secreting masses (n = 16) had a higher average SUVmax of 5.9 compared to nonfunctioning masses (n = 11, average SUVmax 4.2) and aldosterone-hypersecreting masses (n = 5, average SUVmax 3.2) (p = 0.007). SUVmax cut-off of 5.33 had 50.0% sensitivity and 81.8% specificity in localizing a cortisol-secreting mass. GLUT3 expression was 2.19-fold higher in patients with CS compared to patients with nonfunctioning adenomas (p = 0.003) and 2.16-fold higher in patients with CS compared to Conn's syndrome (p = 0.006). GLUT3 immunohistochemistry showed 2.2-fold higher staining in CS tumor samples compared to nonfunctioning adenomas.


CONCLUSIONS
Differential 18F-FDG PET/CT uptake was observed in patients with nonfunctioning, aldosterone-hypersecreting, and cortisol-secreting masses. GLUT3 overexpression in cortisol-secreting tumor likely accounts for the differential uptake. Future larger cohort studies will need to be conducted to determine if 18F-FDG PET/CT uptake can lateralize cortisol-secreting adrenal masses in patients with bilateral adrenal masses.
Endocrine Oncology Branch, Clinical Research Center, National Cancer Institute, NIH, Building 10-CRC, Room 3-5840, Bethesda, MD, 20892, USA.
Dhaval
D
Patel
Endocrine Oncology Branch, Clinical Research Center, National Cancer Institute, NIH, Building 10-CRC, Room 3-5840, Bethesda, MD, 20892, USA.
Sudheer Kumar
SK
Gara
Perelman School of Medicine at the University of Pennsylvania, Philadelphia, PA, 19104, USA.
Ryan J
RJ
Ellis
Endocrine Oncology Branch, Clinical Research Center, National Cancer Institute, NIH, Building 10-CRC, Room 3-5840, Bethesda, MD, 20892, USA.
Myriem
M
Boufraqech
Endocrine Oncology Branch, Clinical Research Center, National Cancer Institute, NIH, Building 10-CRC, Room 3-5840, Bethesda, MD, 20892, USA.
Naris
N
Nilubol
PET Department, Clinical Center, NIH, Bethesda, MD, 20892, USA.
Corina
C
Millo
Eunice Kennedy Shriver National Institute of Child Health and Human Development, NIH, Bethesda, MD, 20892, USA.
Constantine A
CA
Stratakis
Endocrine Oncology Branch, Clinical Research Center, National Cancer Institute, NIH, Building 10-CRC, Room 3-5840, Bethesda, MD, 20892, USA. kebebewe@mail.nih.gov.
Electron
E
Kebebew
D000310:Adrenal Gland Neoplasms / Q000175:diagnosis*; D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010865:Pilot Projects; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000494:pharmacology; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed / Q000379:methods*
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18