However, of the 25 patients who proceeded on to receive HCT, 15 (60%) were in ongoing remission, with a median duration of 35 months (range, 11-55 months). Six patients (24%) experienced transplant-related mortality; four of these patients had no prior HCT. Ten patients (40%) experienced acute graft-versus-host disease (GVHD); two of these patients experienced grade 4 GVHD, and one experienced grade 3 GVHD.
Of the 25 patients who went on to HCT, 19 were receiving their first transplant, with a median time to transplant after CAR T-cell therapy of 57 days. Five patients (20%) had primary refractory disease. Most patients (n = 18; 72%) had TBI-based conditioning prior to their post–CAR T-cell therapy HCT. The median patient age was 15 (range, 5-30) years.
The systematic review included patients from two phase 1 studies; one was of CD19-28z CAR T-cell therapy for children and young adults with B-cell leukemia or lymphoma, and the other was of CD22-41BB CAR T-cell therapy for children and young adults with recurrent or refractory B-cell malignancies expressing CD22.
To weigh the benefit of the combined CAR T-cell therapy/HCT approach, Dr. Shalabi and her colleagues used a competing risk analysis to determine the risk of relapse post-HCT versus the risk of transplant-related mortality. Among patients undergoing their first HCT, the researchers found a 12-month cumulative incidence of relapse of 5.3% with the combined CAR T-cell therapy/HCT approach (95% confidence interval, 0.3%-22.1%). The 24-month cumulative incidence of relapse was 11.3% (95% CI, 1.7%-31.1%).