HLA-Mismatched Microtransplantation Vs HLA-Matched Nonmyeloablative Transplantation for Acute Myeloid Leukemia in Intermediate-Risk: Comparable Survival but Avoids of Gvhd

The optimal therapy for intermediate-risk patients with acute myeloid leukemia (AML) in first complete remission (CR1) is uncertain. Recent studies shown that microtransplantation (MST) can improve survival in AML-CR1 patients. However, a comparison study between the MST and nonmyeloablative stem cell transplantation (NST) is lacking. 156 intermediate-risk AML-CR1 patients aged 9 to 59 years were enrolled in this study. 57 patients who had a HLA-identical donors were assigned to receive NST therapy with graft-versus-host disease (GVHD) prophylaxis. The other 99 who had no HLA-identical donors including 86 family-related, 9 distantly related and 4 unrelated donor were assigned to receive MST therapy but without GVHD prophylaxis. The probabilities of 10-year overall survival and leukemia-free survival was comparable in the MST-group and NST-group (70.7% vs. 61.4% and 59.6% vs. 57.9%). The NST-group exhibited a higher full donor chimerism (96.5%) and higher GVHD (33.3%), whereas the MST-group produced a higher donor microchimerism (75%), slightly higher relapse (32.3% vs. 22.8%) and significantly lower non-relapse mortality (6.9% vs. 19.3%, P=0.021) but without GVHD. In the MST-group, the patients with increase of WT1⁺ CD8⁺ T cells exhibited significantly higher leukemia-free survival and lower relapse than those without (92.0% vs. 40.0%, P=0.003; 8.0% vs. 50%, P=0.009). These results indicate that, compared to NST, MST produced a comparable survival, less transplantation-related mortality, avoidance of clinical GVHD and overcome limitations of HLA-barrier, suggesting a much safe and effective therapy for intermediate-risk AML-CR1, particularly for those without a HLA-identical donor.