Metabolic Activity Measured by F-18 FDG PET in Natural Killer-Cell Lymphoma Compared to Aggressive B- and T-Cell Lymphomas

Purpose: We aim to compare the metabolic activity by F-18 fluorodeoxyglucose (FDG) uptake across the various histologic subtypes of non-Hodgkin lymphoma (NHL) in a single center, with particular interest in the natural killer (NK)-cell lymphoma subtype for which literature is scarce because of the rarity of these lymphomas in Western populations. Materials and Methods: We retrospectively evaluated the FDG-avidity of pretreatment positron emission tomography-computed tomography scans of 117 consecutive NHL patients by measuring the lesion with the highest maximum standardized uptake value (SUV(max)) in each patient. Mean SUV(max) of 4 major groups of NHL; aggressive B-cell (n = 63), indolent B-cell (n = 31), NK-cell (n = 14) and aggressive T-cell lymphoma (n = 9), was compared using one-way analysis of variance. P value <0.05 was considered statistically significant. Results: SUV(max) (mean +/- standard deviation) of NK-cell lymphoma (9.2 +/- 4.5) was significantly lower than aggressive B-cell lymphoma (14.1 +/- 6.4) (P = 0.013), similar to aggressive T-cell lymphoma (7.6 +/- 3.9) and significantly higher than that of indolent B-cell lymphoma (5.3 +/- 3.1) (P = 0.039). Conclusion: The metabolic phenotype, characterized by FDG uptake of the various NHL subtypes is described. Although NK-cell lymphomas demonstrate high metabolic activity, SUV(max) is significantly lower than its aggressive B-cell counterparts. This may reflect the large amount of coagulative necrosis and inflammatory component of the tumor, and the relatively slower tumor growth rate compared with aggressive B-cell lymphomas.