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CAR-T Therapy Shows Efficacy at Eliminating Residual Disease in B-ALL
In a small clinical trial where patients with B-cell acute lymphoblastic leukemia (B-ALL) with minimal residual disease (MRD) were treated with CD19 chimeric antigen receptor (CAR) T-cell therapy, 85.7% (n = 12 of 14) responded, converting to MRD-negativity.
“In standard-risk adult ALL, the median relapse-free survival (rFS) in patients converting to MRD-positive during the early post-consolidation phase is 16.7 months,” wrote lead author Wenyi Lu, Department of Hematology, Tianjin First Central Hospital, Tianjin, China, and co-authors. “Some studies have shown that subjects with low ALL burden have a higher (complete remission) CR rate than those with high ALL burden, which indicates that CAR-T therapy may achieve a better response in MRD-positive patients than refractory/relapsed (R/R) B-ALL patients.
Thus, Dr Lu et al aimed to investigate whether CAR T-cells could eliminate residual leukemia cells and prevent clinical relapse in patients with MRD-positive B-ALL.
In the study, researchers evaluated outcomes from 14 patients with B-ALL, all of whom were in CR, but had detectable MRD after initial therapy. Eight of the patients had persistent MRD, while 6 had MRD relapse. Five were refractory to imatinib or dasatinib. All were treated with CD19 CAR T-cells, and underwent allogenic stem cell transplants (ASCT) immediately thereafter.
At a median follow-up of 647 days, 4 patients experienced a morphologic relapse. Active disease was defined as blasts ≥ 5% or extramedullary disease. The median time to relapse was 418 days (range: 238-740 days). The MRD level of 3 of the patients who relapsed before CAR T-cell therapy was higher than that of the other patients. The 2-year event-free survival (EFS) rate in MRD-positive patients was 61.2% ± 14%, and the 2-year overall survival (OS) was 78.6% ± 11%, which are significantly higher than for patients with active disease.
Moreover, patients with MRD had a lower grade of cytokine release syndrome (CRS) than patients with active disease.
