Treatment-related mortality and recurrence of disease account for the majority of treatment failures in allogeneic transplantation for advanced hematologic malignancies. The most commonly utilized conditioning regimens consist of cyclophosphamide and total-body irradiation or busulfan and cyclophosphamide. Other agents such as etoposide or thiotepa are sometimes added to maximize the antileukemic effect. New conditioning regimens are however still needed to maximize efficacy and limit treatment-related deaths. Over the past several years, the investigators have evaluated several new conditioning regimens that incorporate fludarabine, a novel immunosuppressant that has limited toxicity and that has synergistic activity with alkylating agents. Recent data have suggested that fludarabine may be used in combination with standard doses of oral or IV busulfan, thus reducing the toxicity previously observed with cyclophosphamide/ busulfan regimens.
