Nonablative conditioning in allogeneic stem cell transplantation has been performed for reducing transplantation-related complications. In this study, we compared outcomes of nonablative and ablative conditioning in younger adults less than 50 years with hematologic malignancies. From Jan. 2001 until Dec. 2004 adult patients younger than 50 years old with hematologic malignancies were transplanted from HLA-matched donors, using nonablative conditioning (n ϭ 35) or ablative conditioning (n ϭ

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... The median ages of nonablative and ablative patients were 36 and 33 years, respectively (P ϭ .014). 17% of nonablative patients received a prior myeloablative transplant, whereas none of the ablative patients did (P ϭ .001). Neutrophil engraftment (ie, time to absolute neutrophil count Ͼ0.5 ϫ 10 9 /L) was faster in the nonablative group (median, 10 days; range, 0-21 days) than in the ablative group (median, 18 days; range, 11-38 days) (P Ͻ .0001). The time to reach a platelet count of more than 20 ϫ 10 9 /L was 13 days (range, 0-35 days) in the nonablative group, compared with 22 days (range, 9-110 days) in the ablative group (P ϭ .006). The incidence of grades 2 to 4 acute graft-versus-host disease was similar in patients of nonablative and ablative groups, 17% vs. 24%, respectively (P ϭ .40). 39% of patients in the nonablative group and 36% of patients in the ablative group developed chronic graft-versus-host disease (P ϭ .76). The cumulative incidences of day 100 nonrelapse mortality were 18% in nonablative patients and 21% in ablative patients (P ϭ .88). Overall survival rates for nonablative and ablative patients were 43% and 35% at 2 years (P ϭ .72), respectively. Two-year progression free survival rates of nonablative and ablative patients were both 35%. In conclusion, nonablative transplantation showed comparable outcomes with ablative transplantation for younger patients less than 50 years with hematological malignancies.