Risk Stratification in Pediatric Non-Hodgkin Lymphoma Using Maximum Tumor Dissemination and Metabolic Tumor Burden on Baseline 18F-FDG PET/CT

BACKGROUND: Pediatric non-Hodgkin lymphoma (NHL) is the third most common childhood malignancy, but reliable prognostication remains challenging. This study aimed to evaluate the prognostic value of baseline 18F-FDG PET/CT parameters reflecting disease spread, the largest interlesion distance (Dmax), and total metabolic tumor volume (TMTV), in pediatric patients with NHL. PATIENTS AND METHODS: We retrospectively enrolled 98 pediatric patients with NHL (74 males, 24 females; median age, 10.4 y; range, 0.3-17.9 y) who underwent FDG PET/CT for staging between January 2008 and November 2024. TMTVs were defined using a 41% maximum standardized uptake value threshold. Distances between all lesion pairs were calculated to determine Dmax. Prognostic significance of FDG PET/CT parameters and clinical factors for survival outcomes was evaluated using univariate analysis. RESULTS: Based on surrogate TMTV (sTMTV) and sDmax, patients were stratified into no (n = 61), 1-risk (n = 17), and 2-risk factor groups (n = 20). In the univariate analysis, advanced stage (≥IV), bone marrow involvement, elevated serum lactate dehydrogenase (LDH) level (>500 IU/L), sTMTV, sDmax, and the PET-based risk group were significant prognostic factors for event-free survival (P < 0.05). For overall survival, significant factors included LDH level, sTMTV, sDmax, and the PET-based risk group (P < 0.05). The PET-based risk stratification was also reflected in survival outcomes. CONCLUSIONS: sTMTV and sDmax derived from FDG PET/CT are significant prognostic biomarkers in pediatric NHL. Their combination enables effective stratification of pediatric patients with NHL into distinct risk groups and may inform future risk-adapted management strategies, potentially improving survival in this population.