Splenomegaly Negatively Impacts Neutrophil Engraftment in Cord Blood Transplantation

Delayed neutrophil engraftment (NE) has been reported in cord blood transplantation (CBT) compared with other stem cell transplantation methods. The numbers of total nucleated cells (TNCs), CD34⁺ cells (generally ≥ 1 × 10⁵/kg), and granulocyte/macrophage colony-forming units (CFU-GM) significantly impact NE. Splenomegaly exerts negative effects on NE, but the appropriate cell dose for the patients with splenomegaly has not yet been determined, especially in CBT. We retrospectively investigated the effect of splenomegaly and number of CD34⁺ cells infused on NE through the analysis of outcomes of 502 consecutive patients who underwent single CBT for the first time at Toranomon Hospital between 2011 and 2018. Spleen index, L_max × H_vert (SI L_max × H_vert), was defined as maximal length at any transverse section, (L_max) × vertical height (H_vert), and splenomegaly was defined as SI L_max × H_vert ≥ 115 cm². Our results show that splenomegaly (hazard ratio [HR], .60; P < .01) and low dose of infused CD34⁺ cells (HR, .58; P < .01) had significant negative impact on NE, whereas neither CFU-GM dose nor TNC dose had any impact on NE in multivariate analysis. Other factors with a significant negative impact on NE in multivariate analysis were myeloid disease (HR, .62; P < .01), nonremission status at CBT (HR, .71; P < .01), low Eastern Cooperative Oncology Group Performance Status (HR, .68; P < .01), and graft-versus-host disease prophylaxis (other than tacrolimus alone) (HR, .76; P < .01). Without splenomegaly, even patients infused with < .8 × 10⁵/kg CD34⁺ cells achieved up to 94.3% NE, with the median value observed at 21 days post-CBT. This study shows that splenomegaly has a significant negative impact on NE after CBT. Cord blood units with < .8 × 10⁵/kg CD34⁺ cells may still be a suitable choice for patients without splenomegaly.