Enlarged spleen is associated with low neutrophil and platelet engraftment rates and poor survival after allogeneic stem cell transplantation in patients with acute myeloid leukemia and myelodysplastic syndrome.

Primary graft failure can be a cause of early morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT), as it leads to a high risk of severe infections and bleeding. Splenomegaly is associated with primary graft failure in patients of myelofibrosis, but the association between splenomegaly and outcomes after HSCT in patients with myeloid malignancies has not been previously evaluated. The aim of this study was to investigate the effect of spleen volume on engraftment kinetics in patients with acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS). We enrolled 85 patients. The median spleen volume was 146 cm3 (quartile 88-201 cm3). The adjusted hazard ratios for neutrophil and platelet engraftments were 0.17 (0.07-0.40, p < 0.001) and 0.19 (0.05-0.69, p = 0.011), respectively, for the high-risk group, at a cutoff splenic volume of 320 cm3. Overall survival at 3 years after HSCT was significantly poor in the high-risk group with an adjusted hazard ratio of 13.8 (2.61-72.4, p = 0.002). Enlarged spleen was associated with low neutrophil and platelet engraftment rates and poor survival after allogeneic HSCT in patients of AML and MDS.