FDG altered biodistribution in white adipose tissue, a rare entity: case report and review of the literature.

ABSTRACT

PURPOSE: Altered 18F-fluorodeoxyglucose (FDG) biodistribution due to patient factors such as exercise and inadequate fasting are well established causes of limited diagnostic efficacy. In addition, medications such as G-CSF are known to affect uptake of FDG by bone marrow and spleen. In this study, we present a case of increased white adipose uptake in a pediatric lymphoma patient who recently received high dose dexamethasone and review the relevant literature regarding this rare and poorly understood pattern of altered FDG biodistribution. METHODS: A 14-year-old male patient diagnosed with B-cell lymphoblastic lymphoma underwent FDG-PET/CT for restaging shortly after completing an induction chemotherapy regimen. Images revealed diffuse FDG uptake localizing to white adipose tissue, attributed to the 29-day course of dexamethasone which was completed two days prior. A diagnostically adequate study with relative normalization of FDG biodistribution was obtained seven days later. RESULTS: In our review of the literature, diffuse FDG uptake by white fat is a rare occurrence and has only been reported by a few case reports and early observational studies. In addition to patients receiving corticosteroids, other cases of medication-induced adipose remodeling such as patients receiving highly active antiretroviral therapy have been documented with similar patterns of increased white adipose tissue activity. CONCLUSION: Corticosteroid-induced white fat uptake of FDG is a rare phenomenon that can limit diagnostic accuracy of FDG-PET/CT and necessitate repeat imaging. Current evidence suggests that a wait period of at least one week after discontinuation of corticosteroids is sufficient to allow for decreased white fat uptake and increased diagnostic accuracy.