Results of reduced intensity preparative regimen (RIC) hematopoietic stem cell transplantation (HSCT) in the HLA identical HSCT setting have not been compared to myeloablative HSCT (MA) in patients with AML over 50 years of age. With this aim, outcomes of 315 RIC were compared with 407 MA HSCT recipients from 182 transplant centers. The majority of RIC was fludarabine-based regimen associated to Busulfan (BU) (53%) or low dose TBI (24%). Multivariate analyses of outcomes were used adjusting for differences between both groups. The median follow-up was 13 months. Cytogenetics, FAB classification, WBC count at diagnosis and status of the disease at transplant were not statistically different between the two groups. However, RIC patients were older (median 57 years versus 54 years), transplanted more recently, and more frequently with peripheral blood allogeneic stem cells as compared to MA recipients. In multivariate analysis, Incidence of grade II-IV acute GvHD (aGvHD) was significantly lower after RIC: 22% compared to 31% after MA HSCT (p=0.003) but not Grade III-IV (8% versus 12%, respectively)(p=0.12). the risk of chronic GVHD was lower following RIC (RR=0.69; 95% CI,=0.51 to 0.94, p=0.02). Transplant-related mortality was significantly decreased(18% versus 32%) (p<10−4; RR=0.48, CI= 0.33 to 0.68), and relapse incidence was significantly higher (41% versus 24%) (p=0.0003; RR=1.78, CI=1.3 to 2.43) after RIC transplantation. Leukaemia-free survival (LFS) was not statistically different between the two groups. These results may set the grounds for prospective trials comparing RIC with other strategies of treatment in elderly AML.

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