PET-Based Risk Stratification in Primary Mediastinal B-Cell Lymphoma: A Comparative Analysis of Different Segmentation Methods in the IELSG37 Trial Patient Cohort

Standardizing tumor measurement on ¹⁸F-FDG PET is crucial for the routine clinical use of powerful PET-derived lymphoma prognostic factors such as metabolic tumor volume (MTV) and total lesion glycolysis (TLG). The recent proposal of an SUV of 4 as a new reference segmentation threshold for most aggressive lymphomas may homogenize volume-based metrics and facilitate their clinical application. Methods: This study compared MTV and TLG in primary mediastinal B-cell lymphoma (PMBCL) patients estimated using an SUV of 4 and the current threshold at 25% of SUV_max. Baseline PET metrics were evaluated in 501 PMBCL patients from the IELSG37 trial. Results: Median MTV and TLG estimated with the 25% of SUV_max threshold were significantly lower than those obtained with the new reference threshold; however, an extremely high correlation was observed between the methods for both MTV (r = 0.95) and TLG (r = 0.99), resulting in superimposable prognostic power. Conclusion: These findings support the routine use of an SUV of 4 for volumetric measurements in PMBCL.