Purpose or Case Report: PET/CT plays an important role in assessing response to therapy in patients undergoing treatment for Hodgkin’s lymphoma (HL). A negative PET/CT following completion of chemotherapy has a high negative predictive value (>95%) for disease progression, relapse, or recurrence. Thus treatment decisions, including the decision to pursue radiation therapy or to alter chemotherapy regimens, are often made based on PET/CT results. Given the treatment implications, obtaining accurate PET/CT results is of the utmost importance.
Methods & Materials:
Results: High doses of steroid are used in most HL treatment regimens. Reports in the literature have suggested high steroid doses being given around the time of PET/CT can be associated with altered FDG distribution and accumulation in white fat, thus limiting the interpretability of the PET/CT. We present a series of 4 pediatric HL patients in whom this altered pattern of FDG distribution was observed on PET/CT examinations performed after the patients had completed their HL therapy course and were no longer receiving high dose corticosteroids. We also present results from an additional patient with methylmalonic acidemia, in whom the same altered FDG uptake distribution was observed. These results demonstrate that the “Cushingoid” pattern of altered FDG uptake in subcutaneous white fat can occur even when patients are not actively receiving high treatment doses of steroid, and suggest an alteration in gluconeogenesis as a possible explanation for the altered uptake pattern.
Conclusions: An altered pattern of FDG biodistribution and accumulation in white fat has been observed in patients receiving high dose corticosteroid therapy. The results presented here extend those observations and show that this altered pattern of FDG distribution can also occur following treatment for Hodgkin lymphoma, and may be observed with lower doses of steroid and may occur even after patients are no longer actively receiving corticosteroids. A similar altered distribution of FDG uptake was also observed in a patient with MMA suggesting that alteration in gluconeogenesis may be involved as an underlying mechanism. In the patients with HL, repeat PET/CT examinations performed several days later revealed normalization of FDG distribution. These results indicate that a delay of up to two weeks following the completion of high dose corticosteroid therapy should reduce the residual steroid effects on glucose metabolism and increase the diagnostic yield of re-staging PET/CT examinations.