An update on the usefulness of the intensity of 18fluorodeoxyglucose uptake in positron emission tomography (FDG-PET) in distinguishing between indolent and aggressive non-Hodgkin’s lymphomas

Abstract

8602 Background: FDG PET is recommended for the initial evaluation and staging of patients with non-Hodgkin’s lymphoma (NHL). There is not enough knowledge about the usefulness of PET in distinguishing different subtypes of NHL, so we investigated whether the intensity of tumor FDG uptake in NHL is different between indolent and aggressive histology. This comparison may also clarify the value ot an initial PET scan in indolent lymphoma, because of its lower and unpredictable uptake. Methods: We studied a retrospective cohort of lymphoma patients with NHL, attended at a single tertiary care center from April 2003 to November 2007 and who had not received treatment. We reviewed the initial, re-staging and/or relapse PET studies of 101 patients with diagnosis of NHL. Mean age 45 (15 to 86) years, 41 female and 60 male. We recorded the highest standardized uptake value (SUV), correlations were made with histopathology. We analyzed SUVs considering the various histologies and grades. Two sample comparisons were performed using the Wilcoxon test. Results: The histopathological diagnoses were: diffuse large B-cell lymphomas (53 patients), anaplastic large cell lymphoma (8 patients), Follicular lymphoma grade 1 and 2 (25 patients), Follicular lymphoma grade 3 (5), Burkitt (5), and other types (5 patients, 1 MALT, 1 lymphoma/CLL, 1 mycosis fungoides, 2 peripheral t cell lymphoma). FDG uptake was lower in indolent (29 patients) than aggressive lymphoma (72 patients) (SUV, mean 5.8, SD ± 2.2, mean rank 26.2, sum of ranks 768 vs 13.5 SD ± 6.9, mean rank 60.9, sum of ranks 4388; P=<.0001). Despite overlap between indolent and aggressive disease in the low SUV range (indolent 1.9 to 11; aggressive 3.2 to 33) all cases of indolent lymphoma had an SUV ≤ 11. Conclusions: These findings confirm our previous results showing that the FDG uptake is significantly lower in indolent than in aggressive lymphoma. Patients with NHL and SUV > 11 have a high likelihood for aggressive disease. These results also suggest that to follow the treatment response in indolent lymphoma is important to have an initial PET study. No significant financial relationships to disclose.