Haploidentical Stem Cell Transplantation With Post-transplant Cyclophosphamide for Pediatric Acute Leukemia is Safe and Effective.

Background: Haploidentical family donor is universally available and is fast emerging as an alternative donor choice for children with leukemia needing hematopoietic stem cell transplant (HSCT). Here we describe our experience of treating children with acute leukemia by haploidentical HSCT with posttransplant cyclophosphamide (PTCy).

Methods: We retrospectively analyzed the outcome data of 17 children with acute leukemia who underwent related haploidentical HSCT. Fifteen were in complete remission (CR) before HSCT: CR1-6, CR2-7, and CR3-2 and 2 were not in remission. Donors were mobilized with granulocyte colony stimulating factor. The conditioning was nonmyeloablative in 4 and myeloablative in 13. All received PTCy 50 mg/kg on days 3 and 4 as graft-versus-host disease (GVHD) prophylaxis along with tacrolimus or cyclosporine and mycophenolate mofetil. A median of 8.94 million of CD34+ cells/kg was infused.

Results: All patients were engrafted for neutrophil and platelets, except 1 child with refractory acute myeloid leukemia disease who relapsed before engraftment. Five children relapsed (4 died and 1 child with CD20-positive leukemia is disease free after Rituximab therapy). There was 1 transplant-related mortality due to grade IV GVHD. Remaining 11 patients are in CR. Acute GVHD was seen in 4 patients. Of 4, 3 children later developed chronic GVHD and all are alive and disease free. Three of 4 children who received nonmyeloablative conditioning have relapsed. Overall survival is 70.5% and event-free survival is 64.7%. Median follow-up of all patients was 393 days.

Conclusion: Haploidentical HSCT with PTCy is a safe and effective therapy for children with acute leukemia. Myeloablative conditioning and chronic GVHD lead to improved disease-free survival.