[¹⁸F]FDG-PET/CT in DLBCL-patients treated with CAR-T cell therapy: potential for defining patient prognosis

The aim of this study is to evaluate the potential of [¹⁸F]FDG-PET/CT in terms of prognostic value and treatment monitoring in relapsed / refractory diffuse large B-cell lymphoma (DLBCL)-patients treated with chimeric antigen receptor T-cell (CAR-T) therapy.

Forty-eight [¹⁸F]FDG-PET/CT scans, acquired at pre-defined time points (t₀ - t₂) of 18 DLBCL-patients (mean age: 60 ± 12 years) treated with CAR-T cell therapy were retrospectively enrolled. Median time of follow-up was ten months (IQR 6-16) following CAR-T cell infusion. SUV_max, sum of the product of diameters (SPD), Deauville score (DS) and Lugano classification (LC) were evaluated. Clinical parameters (age, sex) were obtained. Survival time analyses for progression-free survival (PFS) and overall survival (OS) were calculated, the latter by using the Kaplan-Meier method and Cox regression including a hazard ratio (HR). P values below 0.05 were defined as statistically significant. 95 %-confidence intervals (CI) were calculated.

Patients with a SUV_max> 9.0 at t₀ (median as threshold value) had a significantly shorter PFS (p = 0.04) and OS (p < 0.01). According to LC, a progressive disease (PD) at t₁ (p = 0.02) and t₂ (p < 0.01) was correlated with a reduced OS. SUV_max > 9.0 at t₀ (p = 0.03, HR = 7.0, CI: 1.3-40.5) and DS > 3 at t₁ (p = 0.04, HR = 8.2, CI: 1.1-61.3) were associated with an increased risk of a PD.

SUV_max of [¹⁸F]FDG-PET/CT seems to be useful as a prognostic marker in DLBCL-patients undergoing CAR-T cell therapy. Furthermore, scores of clinical established Deauville classification and Lugano response criteria acquired at post-CAR-T [¹⁸F]FDG-PET/CT might be an indicator for early therapy failure.