Long-term follow-up of CD19 chimeric antigen receptor T-cell therapy for relapsed/refractory acute lymphoblastic leukemia after allogeneic hematopoietic stem cell transplantation

Background aims The efficacy of CD19-targeted chimeric antigen receptor T (CAR T) cells for treatment of relapsed B-cell malignancies after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and the long-term outcomes of these patients remain inconclusive. Methods The authors focused on the survival of 35 patients with B-cell acute lymphoblastic leukemia who relapsed after allo-HSCT and received CAR T cells. Results Of the 34 eligible patients, 30 achieved minimal residual disease-negative complete remission (CR), with a total CR rate of 85.7% (79.8–91.6%). There were 14 patients who received various forms of additional therapy after achieving CR. After a median follow-up of 20.7 months, it was noted that 17 patients had relapsed at a median of 4.5 months (2–34 months). The cumulative recurrence rate (RR) at 18 months was 68.3% (57.6–79.0%). Additional treatment did not reduce the RR but seemed to delay the time to relapse (mean: 5.9 months vs 13.1 months; P = 0.046). Patients with a lower tumor burden (≤10%) had a lower RR (25.0% vs 78.6% at 12 months; P = 0.006). The overall survival (OS) rate for the CR patients was 30.0% (20.3–29.7%) at 18 months, with a median OS of 12.7 months. Conclusions The authors’ study indicated that for patients who relapsed after HSCT, although a high CR rate was achieved after CAR T therapy, the long-term efficacy was unsatisfactory. It is necessary to optimize additional treatment, including a second HSCT, to further improve long-term efficacy after CAR T infusion.