Busulfan, cyclophosphamide and fractionated total body irradiation as a preparatory regimen for marrow transplantation in patients with advanced hematological malignancies: a phase I study.

Thirty-six patients with advanced hematologic malignancy were entered into a phase I study designed to define a tolerable dose of busulfan (BU) and cyclophosphamide (CY) combined with 12 Gy of fractionated total body irradiation (TBI) as preparation for marrow transplantation from HLA-identical siblings, 0-1 locus HLA-non-identical family members or autologous cryopreserved marrow. Five of 18 evaluable patients prepared with 8.7 mg/kg of BU and 69 mg/kg CY + TBI developed severe regimen related toxicity (RRT) while none of 15 patients treated with 6.9 mg/kg of BU and 47 mg/kg of CY + TBI developed severe RRT. Ten of the 15 evaluable patients treated on the lower dose level are alive, nine disease-free, 262-737 days (median, 547) post-transplant with a 87% and 67% actuarial probability of survival at 3 and 18 months respectively. Six of the 18 patients treated on the higher dose level are alive disease-free 273-1039 days (median, 668) post-transplant with a 56% and 27% actuarial probability of survival at 3 and 18 months respectively. Eighteen patients were transplanted with allogeneic marrow for chronic myelogenous leukemia beyond chronic phase and acute non-lymphocytic leukemia beyond first remission or in relapse other than first untreated relapse and only one has relapsed posttransplant. It was concluded that a transplant preparative regimen combining 6.9 mg/kg of BU with 47 mg/kg of CY followed by 12 Gy fractionated TBI is well tolerated. The high probability of surviving this regimen and the low early relapse rate in patients with advanced myeloid malignancies is encouraging.