808MO - Value of early post-treatment FDG PET/CT in diffuse large B-cell lymphoma patients receiving chimeric antigen receptor T cell therapy

Background

Chimeric antigen receptor T-cell (CAR-T) was shown to improve patient outcomes in relapsed/refractory diffuse large B-cell lymphoma (DLBCL). Preliminary investigations showed that ¹⁸FDG PET/CT can be beneficial for post-CAR-T prognostication. Thus, we aimed to evaluate the value of one-month post-treatment ¹⁸FDG PET/CT in these patients.

Methods

In this IRB-approved retrospective study, we reviewed 159 CAR-T candidates referred to our department between 2018 and 2023. Of them, 51 had one-month ¹⁸FDG PET/CT. All patients had pathology-proven DLBCL and baseline pre-treatment ¹⁸FDG PET/CTs. SUVs, total metabolic tumour volume (MTV) and total lesion glycolysis (TLG) were calculated. Also, the furthest distance between tumoral lesions (Dmax) and maximum distance to the spleen (Spleen Dmax) were calculated. When applicable, the date of the disease progression and death were documented. Survival analyses were performed for progression-free survival (PFS) and overall survival (OS) prediction.

Results

Patients underwent one-month ¹⁸FDG PET/CTs with a median of 31 days after CAR-T. All had Deauville scores of IV (28%) or V (72%) at baseline. The median PFS and OS were 124 and 184 days, respectively (17 deaths were documented). In one-month scans, 14 (28%) patients showed a complete metabolic response. In patients (37/51) with significant residual disease in one-month scan, PFS and OS were 107 and 188 days, respectively. The overall status (complete vs non-complete response) had no significant prognostication value considering PFS and OS. However, among one-month PET/CT-derived variables, TLG and spleen Dmax were significant predictors of PFS. Also, changes in MTV from baseline were significant. Considering OS, one-month MTV could significantly predict patient survival. It was the only variable that retained its significance (hazard ratio= 8.76; p-value= 0.003) in the multivariate analysis, alongside all clinical (e.g., age, LDH) and baseline PET parameters.

Conclusions

Early ¹⁸FDG PET/CT have a potential value in predicting post-CAR-T survival. Patients with high MTV are more likely to have poor survival. Also, high tumour burden and extent of the disease may predict earlier progression post-CAR-T.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

P. Veit-Haibach: Financial Interests, Institutional, Research Funding, IIS trial support: Pentixapharm; Financial Interests, Personal, Speaker, Consultant, Advisor: Siemens Healthineers, GE Healthcare, Ontario Association of Radiologists, JCA PET/CT Course, German Cancer Center, Taiwan Oncology Society; Financial Interests, Personal, Member, Editor Fee: Springer Nature; Financial Interests, Personal, Member, Reviewer compensation: Wellcome Trust. All other authors have declared no conflicts of interest.