Predictive Value of Pre-Infusion FDG‐PET/CT Parameters for Clinical Outcomes and Toxicities in Relapsed/Refractory (R/R) Large B-Cell Lymphoma (LBCL) Following CAR-T Cell Therapy

Introduction:

CD19-targeting chimeric antigen receptor (CAR) T-cell therapy has demonstrated significant efficacy in patients with relapsed/refractory (R/R) non-Hodgkin lymphoma but is associated with serious adverse effects such CRS and ICANS. Pre-infusion disease burden has been investigated as a potential predictor of clinical outcome and toxicity. FDG-PET/CT derived metabolic tumor volume (MTV) and total lesion glycolysis (TLG) are quantitative indicators of this baseline tumor load. We aim to assess the predictive value of pre-CART PET metrics on outcome and toxicity in R/R large B-Cell Lymphoma (LBCL) following CAR-T cell therapy.

Method:

We conducted a retrospective single site study of 25 consecutive patients with R/R LBCL treated with CAR-T therapy in our institution between May 2020 and October 2022, All patients underwent FDG‐PET/CT imaging pre-CAR‐T infusion (PET-0) and at day 30 post infusion (PET-1). The images were reviewed by two expert lymphoma PET physicians. Metabolic parameters including MTV, TLG (both calculated using a relative threshold of 40%), SUVmax and Deauville score were calculated. PET-1 was classified as complete metabolic response (CMR, Deauville score 1-3) or non-CMR (Deauville score 4-5) as per the Lugano classification.

Results:

25 patients were analyzed , Based on the median MTV (74,6 mL), TLG (379,4), SUVmax (11,8) values, patients were divided into two groups “low” and “high”.

The median follow-up was 12 months. Patients with low pre-infusion MTV and TLG had significantly superior day 30 CMR rates (84,6% vs 25%, p = 0.001 & 80% vs 20%, p = 0.001 respectively). Pre-infusion SUVmax ( p = 0.29 ) and Deauville score ( p = 0.103), however, did not predict response to treatment. In our population, pre-infusion PET parameters were not associated with CRS or ICANS .

Patients with low pre-infusion MTV and TLG had significantly superior PFS (MTV: p=0.02; TLG: p=0.019) and OS (MTV: p=0.017; TLG: p=0.05), Pre-infusion SUVmax had no statistical significant impact on OS ( p = 0.61) or PFS ( p = 0.37)

Conclusion:

In our study, pre-infusion quantitative PET metrics, TLG and MTV, predict response and outcomes of CART therapy in R/R LBCL. Our results highlight the importance of adequate disease control before CAR‐T administration and the value of pre-infusion FDG‐PET/CT as a predictor of outcomes in R/R LBCL patients treated by CAR‐T‐therapy.