Unmanipulated haploidentical hematopoietic stem cell transplantation is an excellent option for children and young adult relapsed/refractory Philadelphia chromosome-negative B-cell acute lymphoblastic leukemia after CAR-T-cell therapy.

Although chimeric antigen receptor T-cell (CAR-T) therapy produces a high complete remission rate among patients with relapsed/refractory B-cell acute lymphoblastic leukemia, relapse remains an urgent issue. It is uncertain whether consolidative haploidentical-allogeneic hematopoietic stem cell transplantation (haplo-HSCT) is suitable for achieving sustainable remission. Therefore, we aimed to assess the efficacy and safety of bridging CAR-T therapy to haplo-HSCT. Fifty-two patients with relapsed/refractory Philadelphia chromosome-negative B-cell acute lymphoblastic leukemia who underwent haplo-HSCT after CAR-T therapy were analyzed. The median time from CAR-T therapy to haplo-HSCT was 61 days. After a median follow-up of 24.6 months, the 1-year probabilities of event-free survival, overall survival, and cumulative incidence of relapse were 80.1% (95% confidence interval (CI), 69.0-90.9), 92.3% (95% CI, 85.0-99.5), and 14.1% (95% CI, 10.7-17.4), respectively, while the corresponding 2-year probabilities were 76.0% (95% CI, 64.2-87.7), 84.3% (95% CI, 74.3-94.3), and 19.7% (95% CI, 15.3-24.0), respectively. No increased risk of 2-year cumulative incidence of graft-versus-host disease, treatment-related mortality, or infection was observed. A pre-HSCT measurable residual disease-positive status was an independent factor associated with poor overall survival (hazard radio: 4.201, 95% CI: 1.034-17.063; P = 0.045). Haplo-HSCT may be a safe and effective treatment strategy to improve event-free survival and overall survival after CAR-T therapy.

Chimeric Antigens Receptor T Cell Therapy Improve the Prognosis of Pediatric Acute Lymphoblastic Leukemia With Persistent/Recurrent Minimal Residual Disease in First Complete Remission.

Background: The presence of minimal residual disease (MRD) is an independent risk factor for poor prognosis in patients with acute lymphoblastic leukemia (ALL). Moreover, the role of chimeric antigen receptor T-cell (CAR-T) therapy in patients with MRD is currently unclear. Methods: We conducted a prospective study to investigate the role of CAR-T therapy in patients with persistent/recurrent MRD-positive ALL in first remission. Results: A total of 77 patients who had persistent/recurrent MRD were included. Of these patients, 43 were enrolled in the CAR-T group, 20 received chemotherapy as a bridge to allogeneic hematopoietic cell transplantation (allo-HSCT), and 14 patients received intensified chemotherapy. MRD negativity was achieved in 90.7% of the patients after CAR-T infusion. Patients who received CAR-T therapy had a higher 3-year leukemia-free survival (LFS) than patients who did not (77.8% vs. 51.1%, P = 0.033). Furthermore, patients in the CAR-T group had a higher 3-year LFS than those in the chemotherapy bridge-to-allo-HSCT group [77.8% (95% CI, 64.8-90.7%) vs. 68.7% (95% CI, 47.7-89.6%), P = 0.575] and had a significantly higher 3-year LFS than those in the intensified chemotherapy group [77.8% (95% CI, 64.8-90.7%) vs. 28.6% (95% CI, 4.9-52.3%), P = 0.001]. Among the patients who received CAR-T therapy, eight were not bridged to allo-HSCT, and six (75%) remained in remission with a median follow-up of 23.0 months after CAR-T infusion. Conclusions: Our findings show that CAR-T therapy can effectively eliminate MRD and improve survival in patients with a suboptimal MRD response.