PB2354 OUTCOME OF PEDIATRIC PATIENTS TREATED WITH CORD BLOOD TRANSPLANTATION IN OUR INSTITUTE

Background: Cord blood (CB) is a unique donor source in hematopoietic stem cell transplantation. 1) It is applicable to HLA mismatched donor‐recipient pairs. 2) The incidence of severe graft‐versus‐host disease (GVHD) is very low in cord blood transplantation (CBT). 3) Potent graft‐versus‐leukemia (GVL) effect is also observed in CBT. Aims: This study aimed to analyze the cause of death in CBT recipients to improve the outcomes. Methods: A total of 35 children received unrelated CBT (n = 37) at our institute from January 2007 to December 2017. Two patients received CBT twice. We analyzed the association between the characteristics of CB and the outcomes in CBT retrospectively. The study was approved by the institutional review board. Results: In this analysis, 18 boys and 17 girls were included. CBTs were performed as 1 st CBT (n = 25), 2 nd CBT (n = 11), or 3 rd CBT (n = 1). The median age of the patients was 3.9 years (range: 0.1–11.9). The underlying disease consisted of hematological malignancy (n = 22), solid tumor (n = 9), and others (inborn errors of metabolism [n = 2], aplastic anemia [n = 1], chronic active Epstein‐Barr virus infection [n = 1], and graft failure after 1 st transplantation [n = 2]). The preparative regimen was myeloablative (n = 30) and reduced‐intensity conditioning (n = 7). HLA‐C locus was examined in 31 cases. HLA allele‐level disparity was as follows: 8/8 match (n = 1), 7/8 match (n = 9), 6/8 match (n = 9), 5/8 match (n = 8), 4/8 match (n = 3), and 3/8 match (n = 1). Killer immunoglobulin‐like receptor (KIR) mismatch pairs (n = 9) were included. As for 6 cases without C locus information, HLA disparity was as follows: 5/6 match (n = 4), 4/6 match (n = 1), and 3/6 match (n = 1). The median of the infused cell number was 6.51 × 10 7 /kg (range: 1.08–50.3 × 10 7 ). Neutrophil engraftment was achieved in 32 patients (86%). The median time of engraftment was 22 days (range: 11–34). Graft failure and early death due to sepsis before engraftment were observed in 3 and 1 patients, respectively. In the 3 patients of graft failure, 1 remained alive and 2 patients died. Grade III‐IV acute GVHD was observed in 4 (13%) engrafted patients, and extensive chronic GVHD was observed in only 1 patient (3%). Of 35 patients, 4 relapsed whose underlying diseases were hematological malignancy (n = 3) and solid tumor (n = 1). Moreover, 3 of 4 patients who relapsed received re‐transplantation, and then 2 patients died and the participant with acute lymphocytic leukemia have sustained remission for more than 2 years. In total, 11 patients died after CBT, out of which 6 patients died from transplant‐related events such as sepsis before engraftment (n = 1), graft failure (n = 1), pulmonary hemorrhage (n = 1), veno‐occlusive disease (VOD; n = 1), cytomegalovirus pneumonia (n = 1), and bronchiolitis obliterans (n = 1). Most of these events were observed in the early phase within 100 days. The other 5 patients died from an underlying disease (acute lymphocytic leukemia [n = 3] or neuroblastoma [n = 2]). Bivariate analysis revealed no significant association between the CB characteristics and the outcomes (transplant‐related mortality (TRM), the severity of GVHD, or disease recurrence). Summary/Conclusion: This study revealed that the incidence of TRM was higher than that of the recurrence of underlying disease. It is necessary to reduce TRM in the early phase after CBT to improve the outcomes in children treated with CBT. Surprisingly, we did not find any impact of HLA disparity on the TRM, the severity of GVHD, or disease recurrence.