Metabolic Characteristics and Prognostic Differentiation of Aggressive Lymphoma Using One-month Post-CAR-T FDG PET/CT

Background: F-18 fluorodeoxyglucose positron emission tomography computed tomography (PET/CT) is used to assess response of non-Hodgkin lymphoma (NHL) to chimeric antigen receptor T cell (CAR-T) therapy. We sought to describe metabolic and volumetric PET prognostic factors at one month post-CAR-T and identify which patients with partial response (PR) or stable disease (SD) are most likely to subsequently achieve complete response (CR), and which will develop progressive disease (PD) and death.

Methods: Sixty-nine patients with NHL received axicabtagene ciloleucel CAR-T therapy. One-month post-CAR-T infusion and PET/CT scans were segmented with a fixed absolute SUV maximum (SUVMax) threshold of 2.5 using a semiautomated workflow with manual modification to exclude physiologic uptake as needed. Metabolic tumor volume (MTV), total lesion glycolysis (TLG), SUVMax, and other lesion characteristics were calculated and associated with risk of PD and death.

Results: Patients with total MTV > 180 cc, presence of bone or parenchymal disease, SUVMax > 10, single lesion TLG > 245 g, or > 2 total lesions had increased risk of death. Patients with total MTV > 55 cc, total TLG > 250 cc, SUV Max > 10, or > 2 total lesions had increased risk of PD. For the subset of 28 patients with PR/SD, higher SUVMax was associated with increased risk of subsequent PD and death. While 86% of patients who had SUVMax ≥ 10 eventually had PD (HR 3.63, 1.13-11.66, p = 0.03), only 36% of those with SUVMax < 10 had PD.

Conclusions: Higher SUVMax at one month post-CAR-T is associated with higher risk of PD and death. SUVMax ≥ 10 may be useful in guiding early salvage treatment decisions in patients with SD/PR at one month.