Abstract
Diffuse large B-cell lymphoma (DLBCL) represents the most prevalent subtype of non-Hodgkin lymphoma in the adult population and is typically associated with an aggressive clinical trajectory. Despite significant therapeutic advancements, a proportion of patients exhibit resistance to first-line chemotherapy, underscoring the need for accurate and early assessment of treatment response to inform prognosis and optimize therapeutic strategies. We describe the case of a 64-year-old male with a medical history notable for ischemic heart disease and metabolic syndrome who presented with abdominal pain and unintentional weight loss. Diagnostic evaluation confirmed a diagnosis of DLBCL, with initial F-fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT), revealing extensive nodal and extranodal disease involvement. Following the completion of six cycles of frontline chemotherapy, end-of-treatment FDG-PET/CT demonstrated substantial resolution of metabolic activity, corresponding to a Deauville score of 2, consistent with a complete metabolic response. The Deauville five-point scoring system is a standardized method for interpreting PET/CT scans in lymphoma, comparing lesion uptake to the mediastinum and liver to assess treatment response. Consequently, no additional consolidation therapy was pursued. This case illustrates the pivotal role of FDG-PET/CT, interpreted using the Deauville five-point scale, as a reliable and clinically relevant modality for evaluating treatment response in DLBCL, thereby facilitating informed decision-making regarding the continuation or cessation of therapy.