Minimizing graft rejection in allogeneic T cell-depleted bone marrow transplantation

Between October 1991 and May 1994, 42 patients were treated with cyclophosphamide, thiotepa, and total body irradiation followed by an allogeneic transplantation of marrow depleted of T cells with soybean agglutinin and E-rosetting. Patients included in this study had acute myelogenous leukemia (13), chronic myelogenous leukemia (12), acute lymphocytic leukemia (nine), Hodgkin's disease or non-Hodgkin's lymphoma (four), multiple myeloma (three), or myelodysplastic syndrome (one). The mean age was 34 (range 8 to 51 years). Nineteen patients had a matched sibling donor and 18 received marrow from 6/6 matched unrelated donors while five received transplants from unrelated donors disparate at one DR locus (5/6 match). Time to granulocyte engraftment (AGC ≤ 500/mm³) occurred at a mean of 16.5 days for related and 11.4 days for unrelated transplant recipients, and was related to the increased use of G-CSF in the unrelated population. There was no correlation with number of mononuclear cells, T cells, or CD34-positive cells infused, the rate of engraftment or the incidence of transplant complications. Multivariate analysis determined that G-CSF administration and a diagnosis other than ALL were the only factors associated with a faster rate of engraftment. Patients receiving unrelated donor transplants, those with ALL, or those who had a low T cell number infused (≤ 8.0 x 10³ cells/kg) experienced delayed hospital discharge. The regimen resulted in excellent rates of engraftment (95.2%) with only one failure to engraft and one graft rejection. The incidence of grade III-IV acute graft-versus-host disease was 0% with sibling and 26.1% with unrelated donors. There were no cases of veno-occlusive disease. Fifty percent of patients are alive with a mean follow-up of 26.4 months. We conclude that this regimen is well tolerated and results in excellent engraftment with a low incidence of severe graft-versus-host disease and few therapy-related toxicities.