Prognostic value of diffusely increased FDG uptake in spleen and/ or bone marrow due to reticuloendothelial system...

The primary objective of this investigation was to evaluate the predictive utility of diffusely increased ¹⁸F-FDG uptake in the spleen or bone marrow in lymphoma patients and explore the correlation between reticuloendothelial system activation and inflammation.

Our retrospective cohort comprised 629 treatment-naïve lymphoma patients with pathological confirmation who received diagnostic 18 F-FDG PET/CT scans between June 2018 and December 2024. The patients cohort with conditions affecting splenic/bone marrow metabolism (e.g., anemia) or focal uptake were excluded, leaving 142 patients. Based on liver uptake, spleen and bone marrow FDG uptake were classified into two groups: diffusely increased FDG uptake (dFDG, n = 67) and normal FDG uptake (nFDG, n = 75). Hematologic parameters (white blood cells, monocytes, neutrophils, platelets) and inflammatory markers (lactate dehydrogenase [LDH], β₂-microglobulin) were recorded within one week of PET/CT. Volumes of interest (VOIs) were delineated for the liver, spleen, and bone marrow to obtain SUVmean values, calculating SLR and BLR. Survival data were obtained via medical records or telephone follow-up. Prognostic factors were assessed using correlation analysis, proportional hazards regression modeling complemented by Kaplan-Meier survival curve estimation.

No statistically significant differences were observed in age, sex, or B symptoms between groups. The dFDG group had more advanced staging (Stage III/IV: 83.6% vs. 52.0%, p < 0.001) and significantly higher inflammatory markers (LDH, β₂-microglobulin, D-dimer; all p < 0.05). SLR positively correlated with LDH, β₂-microglobulin, and D-dimer (all p < 0.05). SLR > 2.221 was an independent risk factor for PFS (HR = 4.660, p = 0.012). Diffuse bone marrow uptake showed low concordance with bone marrow aspiration (kappa = 0.337, p < 0.001), possibly related to inflammation or marrow activation. Multivariate analysis confirmed SLR as an independent predictor of PFS.

Diffuse splenic FDG uptake strongly correlates with systemic inflammation. The SLR emerged as an independent predictor of progression-free survival in our lymphoma cohort. Diffuse bone marrow uptake may involve non-neoplastic factors and requires comprehensive clinicopathological assessment. This study provides new evidence for PET/CT-guided prognostic evaluation in lymphoma.