Prognostic significance of diffuse increased fluorine-18-fluorodeoxyglucose (18F-FDG) uptake within the reticuloendothelial system in lymphoma patients

Background: As constituents of the reticuloendothelial system, the spleen and bone marrow (BM) have been recognized as integral components of the systemic inflammatory response in cancer contexts, thereby serving as predictive indicators for assessing cancer prognosis. Fluorine-18-fluorodeoxyglucose (18F-FDG) 18 F-FDG) positron emission tomography (PET)/computed tomography (CT) has attained widespread utilization for staging, assessing treatment response, and prognostication in lymphoma patients. Several investigations have proposed that focal increased 18 F-FDG uptake in the BM or spleen may correlate with malignant involvement in lymphoma. However, scant data exist regarding the implications of diffuse BM and splenic uptake. This study aimed to explore the relationships between metabolic parameters of the spleen and BM on 18 F-FDG PET/CT and inflammatory markers, and to assess their prognostic value in patients with lymphoma. Methods: A retrospective analysis was conducted on 118 patients newly diagnosed with malignant lymphoma, who underwent 18 F-FDG PET/CT and exhibited diffuse increased splenic or BM uptake in 18 F-FDG PET/CT imaging. The mean standardized uptake value (SUV) of the spleen, BM, and liver was calculated. The association between metabolic variables and systemic inflammatory markers was investigated, and the prognostic significance of clinicopathological and PET parameters was assessed using overall survival (OS) and progression-free survival (PFS). Results: A statistically significant correlation was found between the spleen-to-liver SUV ratio (SLR) and inflammatory markers such as C-reactive protein (r=0.264, P=0.007) and platelet-to-lymphocyte ratio (r=0.227, P=0.021). No significant correlation was observed between BM-to-liver SUV ratio (BLR) and hematologic parameters, while concordance analysis revealed a fair agreement between BLR and bone marrow biopsy (BMB) (Cohen's Kappa-kappa =0.271, P=0.002). In patients with aggressive non-Hodgkin lymphoma, both SLR [P=0.017, HR 2.715, 95% confidence interval (CI): 0.875-8.428] and BLR (P=0.044, HR 0.795, 95% CI: 0.348-1.813) were significantly linked to OS, while SLR (P=0.019, HR 2.223, 95% CI: 1.139-4.342) emerged as a significant prognostic factor for PFS. Conclusions: This study highlighted that diffuse increased splenic 18 F-FDG uptake in lymphoma patients was closely associated with inflammation, whereas diffuse BM uptake was likely attributable to BM infiltration rather than inflammatory changes. Furthermore, both parameters held promise as prognostic indicators for patients with aggressive lymphoma.