Simple SummaryThe prognostic stratification of patients affected by lymphomas is critical, and many positron-emission tomography (PET) metabolic parameters such as SUV, MTV, and TLG have been studied for this purpose. However, the lack of technical standardization in their measurements strongly affects their clinical power and potential integration into clinical practice. Dmax is a new biomarker that measures the distance between the two farthest hypermetabolic PET lesions and seems to show high accuracy as a prognostic factor in patients with lymphomas. The aim of this systematic review was to provide an evidence-based overview of the role of Dmax in lymphomas.AbstractRecently, several studies introduced the potential prognostic usefulness of maximum tumor dissemination (Dmax) measured by 2-deoxy-2-fluorine-18-fluoro-D-glucose positron-emission tomography/computed tomography (18F-FDG PET/CT). Dmax is a simple three-dimensional feature that represents the maximal distance between the two farthest hypermetabolic PET lesions. A comprehensive computer literature search of PubMed/MEDLINE, Embase, and Cochrane libraries was conducted, including articles indexed up to 28 February 2023. Ultimately, 19 studies analyzing the value of18F-FDG PET/CT Dmax in patients with lymphomas were included. Despite their heterogeneity, most studies showed a significant prognostic role of Dmax in predicting progression-free survival (PFS) and overall survival (OS). Some articles showed that the combination of Dmax with other metabolic features, such as MTV and interim PET response, proved to better stratify the risk of relapse or death. However, some methodological open questions need to be clarified before introducing Dmax into clinical practice.