Effect of steroid use during chemotherapy on SUV levels in PET/CT

Objectives Elevated serum glucose alters SUV values in normal and neoplastic tissue, and can be elevated by steroids. Therefore, we avoid performing 18F-FDG PET scans on patients with serum glucose levels greater than 200 mg/dL. Here we evaluated the effect of prednisone given as part of chemotherapy on physiologic FDG uptake, comparing cohorts of euglycemic and borderline hyperglycemic patients.

Methods A retrospective review of patients undergoing PET/CT for a new diagnosis of lymphoma from 2006-2011, who meet the criteria for our study, was performed. Patients were divided into a euglycemic group (EG) and a hyperglycemic group (HG) based on fasting glucose prior to initial PET/CT (cut-off 150 mg/dl). SUVmax was measured in the cerebellum, ascending aorta, liver, and the anterior compartment of both thighs before and during chemotherapy with prednisone. Serum glucose was checked before the follow-up PET/CT.

Results 20 patients were in the EG, and 16 patients were in the HG. In all patients (age: mean 60.0+/-14.0 years; 24 male), the mean increase in serum glucose was 24.6+/-28.0 mg/dL (all < 200 mg/dl). Among the EG, the glucose increase was less pronounced (5.2+/-14.6 mg/dL) than in the HG (48.8+/-20.8 mg/dL) (p<.0001). The difference in SUV values before and after prednisone usage, however, did not show a statistically significant difference between EG and HG in the aorta, liver or thigh. However, in the cerebellum a higher baseline glucose before treatment with prednisone was associated with a decrease in SUV after prednisone administration (mean difference euglycemic group: 0.69+/-2.3; hyperglycemic group: -1.16+/-2.6; p=0.03).

Conclusions SUV in patients undergoing treatment with corticosteroids should be comparable between their pretreatment and treatment PET/CT as long as the glucose is below 150 mg/dL. Our results suggest that glucose metabolism in tumors, which mimic cerebellar activity, may show an artificial drop in tumor metabolism (SUV) in patients undergoing corticosteroid treatment