Haploidentical Peripheral Blood Stem Cell Transplantation with Post-Transplantation Cyclophosphamide in Children with Advanced Acute Leukemia with Fludarabine-, Busulfan-, and Melphalan-Based Conditioning.

Post-transplantation cyclophosphamide (PTCY) therapy has made haploidentical transplantation a global reality in adults, but the literature is largely silent on the feasibility of this approach in children. We conducted a prospective study of 20 patients (median age, 12 years; range, 2-20 years) with advanced acute leukemia to evaluate the feasibility of PTCY-based haploidentical peripheral blood stem cell (PBSC) transplantation in children. The conditioning regimen comprised fludarabine, i.v. busulfan, and melphalan (Flu-Bu-Mel). PTCY on days +3 and +4 was followed by mycophenolate mofetil for 14-21 days and cyclosporine for 60 days. Thirteen patients (65%) had refractory or relapsed myelogenous leukemia, and the remainder had high-risk lymphoblastic leukemia. Prompt engraftment was noted at a median of 14 days, with full donor chimerism by day +28. The cumulative incidence of acute and chronic graft-versus-host disease was 35% and 5%, respectively. Nonrelapse mortality at 1 year was 20%. The incidence of disease progression was 25.7%. The actuarial overall survival at 2 years was 64.3% (95% confidence interval, 53.4%-75.2%). Our data suggest that Flu-Bu-Mel-based conditioning followed by PTCY-based haploidentical PBSC transplantation with reduced duration of immunosuppression is feasible in pediatric patients with advanced leukemia.

Haploidentical transplantation in children with unmanipulated peripheral blood stem cell graft: The need to look beyond post-transplantation cyclophosphamide in younger children.

Haploidentical transplantation with PTCY following marrow or PBSC graft has been associated with low incidence of GVHD in adults with similar data lacking in children. We report on the outcome of 25 patients <20 yr of age (median age 12 yr), undergoing a haploidentical PBSC transplantation for both malignant and non-malignant disorders. Engraftment was prompt and sustained. Cumulative incidences of acute GVHD and chronic GVHD were 40.3% and 16.7%, respectively. On subgroup analysis, it was evident that acute GVHD developed in 80% of patients <10 yr compared to only 13.3% in those between 10 and 20 yr [log-rank p = 0.001], despite similar graft composition with significantly higher NRM (60% vs. 0%; p = 0.001). The FFS was 63.5%; (79% in >10 yr and 40% in <10 yr, p = 0.01). Our data suggest that PTCY-based haploidentical PBSC transplantation is feasible in older children, but results in early and severe alloreactivity in younger children. These findings, despite being counterintuitive, could be explained by the variable metabolism of CY and oral mycophenolate in younger children indicating that PTCY-based approach as used in adults might not be adequate for younger children.

Hemophagocytic syndrome following haploidentical peripheral blood stem cell transplantation with post-transplant cyclophosphamide.

Hemophagocytic syndrome (HPS) is a rare but serious complication after allogeneic transplantation which has been reported to be particularly high after unrelated cord blood transplantation. We report on the incidence, risk factors and outcome of HPS in 51 patients (age 2-64 years) after haploidentical peripheral blood stem cell (PBSC) transplantation with post-transplantation cyclophosphamide (PTCY). The incidence of HPS was 12.2 %, occurring at a median of 18 days. The non-relapse mortality in patients with HPS was 83.3 % compared to 11.6 % in patients without HPS. Complete donor chimerism was documented in all patients with HPS. Definite infective etiology was identified in two patients only. The others were refractory to multiple lines of treatment and 3 patients underwent a second transplant. Even though the symptoms and biochemical markers of HPS showed prompt response in 2/3 patients undergoing a second allograft, they succumbed to infections before haematological recovery. The others succumbed to multi-organ failure or infections. Age < 10 years, transplantation for non-malignant disease and high CD34 content of the graft were identified as risk factors for HPS. Considering the fact that post-transplant HPS is usually a refractory and fatal condition, we discuss further attempts at deciphering the pathogenesis, developing modalities to prevent this complication and improve the outcome.

Paternal bone marrow infusion as salvage therapy for severe GVHD following maternal haploidentical transplantation resulting in biparental chimerism.

We describe a case of severe GVHD in a 3-year-old child who had received a maternal haploidentical allograft for thalassemia major, which was refractory to several lines of therapy, including weekly infusion of mesenchymal cells. The child was infused paternal marrow graft from which T cells were depleted using Campath 'in the bag' without conditioning. There was significant improvement in gut and liver GVHD over the next few weeks along with persistent mixed biparental chimerism before the child succumbed to CMV pneumonitis. This approach hints at the possibility of using parental TCD marrow to salvage GVHD caused by a graft from the other parent, and raises the possibility of biparental grafting along the same lines as double cord transplantation.