E5316. Role of FDG PET/CT to Evaluate the Effects of Chimeric Antigen Receptor T-Cell Therapy on Spleen in Patients with Non-Hodgkin Lymphoma
  1. Shashi Singh; Stanford University
  2. Rajshree Singh; Mercy Catholic Medical Center
  3. Bimash Shrestha; KIST Medical College
  4. William Raynor; Rutgers Robert Wood Johnson Medical School
  5. Thomas Werner; Hospital of the University of Pennsylvania
  6. Mona-Elisabeth Revheim; The Intervention Center, Rikshospitalet, Division for Technology
  7. Abass Alavi; Hospital of the University of Pennsylvania
Chimeric antigen receptor T-cell (CAR T) therapy is FDA-approved immunotherapy for relapsed or refractory non-Hodgkin lymphoma (NHL). The spleen is involved in approximately one-fifth of the patients with NHL as an extranodal secondary lesion or accompanying disease. On FDG PET/CT, lymphomatous involvement of the spleen may appear as diffusely increased splenic uptake and/or focal increased accumulation of the tracer with or without corresponding hypodense lesions on the CT part of the PET/CT study. CAR T therapy has been shown to ameliorate splenomegaly and early suppression of metabolic activity on FDG PET/CT both in absolute quantification and relative liver metabolism. In this study, we aim to assess the effects of CAR T therapy on the spleen in patients with non-Hodgkin lymphoma.

Materials and Methods:
We included pretreatment and 30–90-day posttreatment FDG PET/CT scans of 60 patients between the ages of 29 and 81 years (mean = 60.3 ± 12.48; 38 men, 22 women) who underwent CAR T therapy for relapsed or refractory NHL. Out of 60 patients, 110 scans of 55 patients were analyzed retrospectively. Five patients were excluded from the study (three patients had the baseline scan performed at an outside institution, one patient because of asplenia, and one was an outlier). EMRs were accessed to identify the type of lymphoma and response to treatment. Participants received CAR T infusion with one of four different types of CAR T therapy in different phases of trials between 2018 and 2021. OsiriX MD software v. 12.5.2 (Pixmeo SARL, Bernex, Sweden) software was used to measure the global mean standardized uptake value (SUVmean) of the spleen in FDG PET/CT scans before and after CAR T infusion.

The average SUVmean of spleen before treatment was 1.96 ± 0.65 (range 1.28–4.37) compared to 1.77 ± 0.37 (range 0.87–2.90) after treatment. The mean difference of posttreatment and pretreatment global SUVmean was 0.22 with SD of 0.66 (p = 0.018). The calculated global spleen SUVmean uptake decreased after initiation of treatment in 33 (60%) and increased in 22 (40%) of the cases.

CAR T therapy is a promising therapeutic approach for treating splenomegaly due to focal or global involvement of lymphoma. Our results showed a significant decrease in splenic FDG uptake from baseline to posttreatment in NHL patients who underwent CAR T therapy. This decrease in FDG uptake in the spleen could indicate decreased splenic metabolism secondary to decreased tumor activity.