Standardization of Quantitative Response Assessment in Lymphoma: A Proposal Based on Findings from Two Prospective Multicenter Trials and Real-World Data

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Ziel/Aim: Positron emission tomography (PET) with 18 F-fluorodeoxyglucose ( 18 F-FDG) plays an important role in response evaluation of lymphoma, which is commonly based on the Deauville scale. Approaches using tumor-to-liver standardized uptake value (SUV) ratios may yield more objective and reproducible results than purely visual assessment. This study examined which volume of interest (VOI) dimensions offer a reliable basis for quantitative image interpretation. Methodik/Methods: We evaluated a total of 90 response assessment PET scans, visually classified as Deauville score 4. Our analysis set consisted of individuals with diffuse large B-cell lymphoma and pediatric Hodgkin lymphoma ( n =30 each) treated in the prospective multicenter trials PETAL and EuroNet-PHL-C2. Furthermore, a real-world cohort of adult Hodgkin lymphoma patients ( n =30) was included. Maximum SUV and average 18 F-FDG uptake were determined for the most active lesion using VOIs of four voxels, 0.2 mL, 0.5 mL, 1.0 mL, and 2.0 mL. Based on the mean liver SUV, we then calculated quantitative PET (qPET) signals as ratios between residual tissue and background for all six measurements. Changes across VOI sizes, their clinical relevance, and the effects of correction factors were analyzed with a linear mixed model fitted to log-transformed data. Ergebnisse/Results: Our analysis demonstrated significant changes in qPET signal across increasing VOI sizes ( P <0.0001). When the previously published thresholds were applied, a considerable proportion of patients shifted to different quantitative Deauville scores. We observed the highest misclassification rate for the 2.0-mL measurements, with 46.7% of individuals being incorrectly categorized as PET-negative. After implementation of volume-specific correction factors, quantitative Deauville scores remained largely unaffected up to 0.5 mL. With VOIs of 1.0 mL and above, variability increased and the adjusted values became less reliable. Schlussfolgerungen/Conclusion: The measured 18 F-FDG signal of residual tissue is underestimated when using larger VOIs. This can be compensated by adjustment factors, which enable sufficiently accurate assignment of a quantitative Deauville score for volumes up to 0.5 mL. Larger VOIs introduce high variability and are not recommended in the context of lymphoma response evaluation. Publication History Article published online: 02 April 2026 © 2026. Thieme. All rights reserved. Georg Thieme Verlag KG Oswald-Hesse-Straße 50, 70469 Stuttgart, Germany

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