Conditioning regimens aredesigned to destroy tumor cells resistant to conventional doses ofchemotherapy without causing fatal nonhematologic organ toxicity. Inpatients undergoing allogeneic stem cell transplantation, conditioningregimens must be sufficiently immunosuppressive to prevent the recipientfrom mounting an immune response capable of rejecting the graft. Graftrejection is uncommon, but this complication is associated with a direoutcome and the risk increases with the degree of mismatch.

There are few randomizedtrials comparing different ablative regimens; in general, increasedintensity of the conditioning regimen may decrease relapse rates, butusually (though not always) at the expense of increased nonrelapse morbidityand mortality. The following represent some of the more common regimens usedtoday, although different combinations and doses may be used at differentcenters. It is essential to check the specific protocol that applies to thepatient for drugs, doses, frequency, and other specifics of treatments.Biologic agents such as Campath® or antithymocyte globulin (ATG)may be added to enhance immunosuppression. See Appendix for ideal bodyweight (IBW) and adjusted ideal body weight (AIBW) for obese patients. Table6.1 summarizes currently used regimens.