Treatment plan
Re-induction CloEC chemotherapy consisted of clofarabine 40 mg/m2/day, etoposide 100 mg/m2/day, and cyclophosphamide 340 mg/m2/day, and it was given on five consecutive days. Children responding to the first course of CloEC received the second course and proceeded to transplantation. Children not responding to the first course were given the second course, and if that did result in fulfillment of the transplant criteria, an additional (third) course of CloEC was administered pending transplantation. Children not responding to the second course entered the palliative care program. Those with > 5% blasts on day 21 after the beginning of the first course were immediately started on the second course. Those with ≤ 5% blasts in hypoplastic bone marrow (BM) were re-evaluated once a week until regeneration occurred or the blasts increased, and then proceeded to the second course. The minimum interval between CloEC courses was 21 days.
The conditioning regimen consisted of clofarabine 200 mg/m2 or fludarabine 150 mg/m2, thiotepa 10 mg/kg, and melphalan 120 mg/m2, and it was given between days –8 and –1 prior to grafting. Serotherapy with ATG (Fresenius) at a total dose of 30 mg/kg was administered from day –12 to day –10 before grafting. For patients with ALL, the preferred donor was always the mother if there was no medical contraindication for donation. For AML patients, donor selection was based on KIR mismatch: if mismatch was observed, the mother was the first choice and the father second choice; if no mismatch was present, the mother was chosen. The donors were screened, evaluated, and accepted by an independent team of adult hematologists.
Peripheral blood stem cells were mobilized with G-CSF, and all donors were harvested twice. The collected cells were processed with the CliniMACS system for immunomagnetic cell separation (Miltenyi Biotec, Gladbach, Germany). The first harvest entailed selection of CD34+ cells, whereas the second harvest was for depletion of T cells expressing the αβ chains of T cell receptor (TCR). Maximum allowed dose of TCR αβ+ cells was set at 5 x 105 cells/kg. A single dose (375 mg/m2) of anti-CD20 antibody (Rituximab) was administered on day +1 after grafting instead of performing B-cell depletion in vivo. Graft-versus-host prophylaxis included the above-mentioned serotherapy, graft processing, and a short course of MMF 600 mg/m2 tid given from day –1 to day +28 if the number of residual αβ TCR positive cells in the graft exceeded 2.5x104/kg of donor’s body weight.