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 (SUVmax) in each patient. Mean SUVmax 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: SUVmax (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, SUVmax 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.