Risk factors associated with host comorbidity:
(1) older recipient age (> 40 or >= 21 years)
(2) decreased pre-transplant performance status
(3) longer duration between diagnosis to transplant (possibly suggesting end-stage disease)
(4) diagnosis of a malignancy other than leukemia
Risk factors associated with graft vs host disease (GVHD):
(1) acute GVHD (Grade II to IV)
(2) HLA disparity between the donor and recipient
Risk factors associated with chemical or radiation toxicity:
(1) methotrexate for GVHD prophylaxis
(2) total body irradiation >= 1200 cGy
(3) myeloablative conditioning
(4) high dose 1-3 bis chloroethyl-1 nitrosurea
