Positron Emission Tomography/Magnetic Resonance (PET/MR) can be a viable imaging technique for chimeric antigen receptor (CAR) T-cell therapy assessment in large B-cell lymphoma (LBCL), a recently published study in Cancer Imaging showed.

CD19-targeted CAR T-cells have effectively treated relapsed/ refractory (r/r) large B-cell lymphomas (LBCL), the researchers noted. Currently, there is no study utilizing 18F-FDG positron emission tomography/computed tomography (CT) to evaluate CAR T-cell therapy’s effectiveness in patients with lymphoma, they added. MR also provides valuable information about the tumor without the need for exposure to ionizing radiation, the investigators continued.

Read more about diffuse large B cell lymphoma therapies

The inclusion criteria for participation in this single-center prospective study were based on the relapsed/refractory CD19+ B-cell lymphoma with no other treatment option available, measurable disease at the inclusion, and Eastern cooperative oncology group performance status score in the range of 0 to 2. The team included 24 patients in the study with an average age of 63 years, including 13 females, with CAR T-cell therapy received from November 2017 to January 2020. 

Study results revealed that of the 24 treated patients, 6 patients didn’t show measurable disease on imaging. One patient showed equipment failure during pretherapy PET/MR imaging, and 1 patient underwent PET/CT imaging due to MR contraindications. Moreover, the study found an association between total tumor burden structural and metabolic metrics with progression-free survival (PFS) and overall survival (OS). 

The results suggested that whole-body FDG PET/MR with diffusion-weighted imaging can be a promising tool in predicting CAR T-cell therapy response in patients with r/r LBCL. Furthermore, total metabolic tumor burden, tumor apparent diffusion coefficient, and FDG uptake in the bone marrow can be possible PET/MR parameters for PFS and OS prediction.

The authors acknowledged several limitations in their study, including the small sample size of 16 participants, which did not allow for multivariable statistical analysis, many of the extracted metrics used were correlated and interchangeable, the exploratory nature of the study, the use of uncorrected p-values, the lack of bone marrow biopsies and the use of an investigational product for CAR T-cell therapy. They suggested that further larger studies should be carried out to confirm these results.

“The findings from this explorative study suggest that PET/MR can be a feasible imaging modality for CAR T-cell therapy evaluation in LBCL, and that a combination of FDG PET/MR derived imaging metrics may be useful for therapy outcome prediction,” the authors concluded.

Reference

Sjöholm, T, Korenyushkin, A, Gammelgård, G. et al. Whole body FDG PET/MR for progression free and overall survival prediction in patients with relapsed/refractory large B-cell lymphomas undergoing CAR T-cell therapyCancer Imaging. Published online December 27, 2022. doi: 10.1186/s40644-022-00513-y