Intensity of ¹⁸fluorodeoxyglucose uptake in positron emission tomography distinguishes between indolent and aggressive non-Hodgkin's lymphoma

Purpose: ¹⁸Fluorodeoxyglucose positron emission tomography (FDG PET) is widely used for the staging of lymphoma. We investigated whether the intensity of tumor FDG uptake could differentiate between indolent and aggressive disease. Materials and Methods: PET studies of 97 patients with non-Hodgkin's lymphoma who were untreated or had relapsed and/or persistent disease and had not received treatment within the last 6 months were analyzed, and the highest standardized uptake value (SUV) per study was recorded. Correlations were made with histopathology. Results: FDG uptake was lower in indolent than in aggressive lymphoma for patients with new (SUV, 7.0 ± 3.1 v 19.6 ± 9.3; P < .01) and relapsed (SUV, 6.3 ± 2.7 v 18.1 ± 10.9; P = .04) disease. Despite overlap between indolent and aggressive disease in the low SUV range (indolent, 2.3 to 13.0; aggressive, 3.2 to 43.0), all cases of indolent lymphoma had an SUV ≤ 13. A receiver operating characteristic (ROC) analysis demonstrated that the SUV distinguished reasonably well between aggressive and indolent disease (area under ROC curve, 84.7%), and an SUV > 10 excluded indolent lymphoma with a specificity of 81%. With a higher cutoff for the SUV, the specificity would have been higher. Conclusion: FDG uptake is lower in indolent than in aggressive lymphoma. Patients with NHL and SUV > 10 have a high likelihood for aggressive disease. This information may be helpful if there is discordance between biopsy and clinical behavior.