||Recipient preparation: The development of aggressive preparative regimens has improved
outcome by reducing the incidence of rejection and relapse. These regimens have increased
antitumor or antileukemic potential as well as delivered superior myeloablation, necessary
to destroy the host marrow and make room for the donor graft without compromising the
marrow stromal elements essential for engraftment. Preparative regimens also suppress the
patient's immune system to allow for acceptance of the graft.
Patients are given high
dosages of cyclophosphamide and/or total body irradiation in standard preparation
regimens. The rejection rate is < 5% in transplants for leukemia patients from
HLA-identical donors. For multiply transfused patients with aplastic anemia, the rejection
rate has also been significantly decreased because of increased immunosuppression during
transplant induction. The two most common preparative regimens are high-dosage
cyclophosphamide (eg, 60 mg/kg/day for 2 days) and total body irradiation or a regimen of
busulfan (eg, 4 mg/kg/day for 4 days) and cyclophosphamide without total body irradiation.
Other drugs (eg, etoposide and cytarabine) are sometimes added to these transplant
regimens to maximize antitumor properties, myeloablation, and immunosuppression.