Retransplantation with Stem Cells from Mismatched Related Donors after Graft Rejection in Pediatric Patients

Graft failure is a rare but life-threatening complication after transplantation of hematopoietic stem cells. Treatment comprises immunoablative reconditioning regimens and a second stem cell donation from the same or from a different donor as soon as possible to minimize the time of pancytopenia and its sequelae. We report a cohort of 11 pediatric patients with leukemias (acute lymphatic n=4, acute or chronic myeloic/MDS n=4) and severe aplastic anemia (n=3) who experienced graft rejection after TBI, busulphan or melphalan based myeloablative transplantation from mismatched related donors (MMRD) (n=6) or after cord blood/matched unrelated donor (MUD) transplantation (n=5) between 2000 and 2006. In the latter the original donor was not available a second time. Thus, all patients were re-transplanted with CD34+ positive selected or CD3/CD19 depleted stem cells from a second, haploidentical parental donor (MACS method, Miltenyi Biotec). Median time span from diagnosis of graft rejection to second donation was 16 days. The reconditioning regimens consisted of total lymphoid irradiation or cyclophosphamide, thiotepa (5mg/kg), fludarabine (120 mg/m2) and ATG/OKT3. A median number of 25×106/kg of body weight stem cells with 60.000/kg residual T cells were infused. Mofetilmycophenolat was given as GvHD prophylaxis, if residual T cells exceeded 25 000/kg bw. Sustained engraftment was achieved in all patients (ANC>500/μl: 9 (11–32) days). No GvHD > grade II was observed. T cell recovery was delayed, however no lethal viral infection occurred. Severe organ toxicity was observed in 2 patients (BOOP, hemorrhagic cystits) and moderate mucositis in 11 patients. 8/11 patients are disease free (median follow up 1.5 (0.3–6.6) years; 1 year EFS=73%). Causes of death were: BOOP (n=1), infection (n=1); only one patient with refractory AML relapsed. Thus, transplantation of stem cells from haploidentical donors represents a realistic option to rescue patients with graft failure within a short time span and for whom a second donation of the original donor is not available. The use of a different donor may help to avoid a second rejection.