Allogeneic stem cell transplantation (BMT) for AML and MDS following i.v. busulfan and cyclophosphamide (i.v. BuCy).

Pretransplant conditioning therapy with i.v. BuCy followed by allogeneic hematopoietic stem cell transplantation (BMT) was investigated in a phase II trial in patients with acute myeloid leukemia (AML) or myelodysplastic syndrome (MDS). We gave i.v. Bu at a dose of 0.8 mg/kg every 6h x 16 doses, followed by Cy 60 mg/kg daily for 2 days. Twenty-six AML patients (18 males/eight females) were treated, only eight of whom were in CR1. The rest were either refractory to induction chemotherapy (four patients) or in a more advanced stage of their disease (14 patients). In addition, nine patients with MDS (1M/8F) were treated. Their median age was 41 years (range 21-64). Engraftment to > or =500 neutrophils/microl was reached at 14 days (range 10-29 days) post BMT, and the median time of neutropenia was only 11 days (range 4-28 days). The most common regimen-related toxicity was grade 2-3 nausea. In the post-BMT period (including BMT day +30), two patients died, one each from pulmonary hemorrhage secondary to CMV pneumonia and hepatic veno-occlusive disease (VOD), for an early treatment-related mortality (TRM) of 5.7%. Three patients developed VOD and two of them died. There was no direct regimen-related pulmonary or neurologic toxicity. Overall, the clinical side-effect spectrum was analogous to what would be expected from a high-dose oral Bu-based regimen; there was no unique toxicity experienced with the used solvent system. The disease-free survival in the high-risk subgroup (all patients not in CR1) at 1 and 2 years post transplant was 44% and 31%, respectively. The 13 patients still alive in CR have been followed for a median of 24 months (range 18-32). Pharmacokinetic analysis showed very good interdose reproducibility, and limited interpatient variability in area under the plasma concentration vs time curve, peak concentration, and clearance of Bu after this i.v. formulation. We conclude, that this new i.v. Bu formulation is well tolerated; it has an impressive safety profile, and we suggest that it should be considered as appropriate replacement for oral busulfan in pretransplant conditioning therapy prior to allogeneic BMT for patients with AML or MDS.