Spleen Status and Engraftment After Allogeneic Hematopoietic Stem Cell Transplantation (HCT).
Authors: Akpek Gorgun , Pasquini Marcelo C , Agovi Manza-A , Logan Brent , Cooke Kenneth R. , Maziarz Richard T , Gupta Vikas , Lazarus Hillard M. , Hale Gregory A. , Marks David I. , Maharaj Dipnarine , Popat Uday , Carabasi Matthew , Bornhaeuser Martin , Bolwell Brian J. , Ringden Olle , Ballen Karen K , Rizzo J. Douglas , McCarthy Philip L. , Ho Vincent T 
Published: October 2019

Abstract
Abstract 3486
Delayed myeloid engraftment after HCT is a risk for increased morbidity and mortality, especially in patients with splenomegaly (SM) at time of transplant. Time to engraftment and overall survival after HCT have not been well analyzed in patients with prior splenectomy (SP) or splenic irradiation (SI), when compared to patients with normal spleens (NS) or with SM. A total of 9,683 recipients with myeloproliferative diseases and/or myelodysplasia who were reported to CIBMTR after receiving a myeloablative allogeneic HCT between 1990 to 2006 were compared according to the spleen status at transplant: 472 SP; 300 SI; 1,471 SM and 7,440 NS. Recipients of cord blood grafts were excluded. The median age was 39 years for all groups, the SP group had a higher proportion of patients with Karnofsky performance score <90%, irradiation-based conditioning and T-cell depleted grafts than the NS group. SI was more frequently administered before 1994 and patients in this group were more likely to receive bone marrow (BM) grafts from HLA-matched siblings donors compared to the other groups. Median follow-up for survivors was 100 months. Speed of engraftment was analyzed by multivariate logistic regression at days 14, 21 and 28 for neutrophils, and days 28 and 60 for platelets. Median times of neutrophil engraftment (NE) were 15 and 18 days, and platelet engraftment (PE) were 22 and 24 days for the SP and NS groups, respectively. Cumulative incidences of NE and PE at day+100 were not different across all four groups, the odds of NE at day 14 and 21 and PE at day 28 were significantly higher for the SP group and lower for SM group (table). There was no significant difference in day 28 PE between SI and NS. Among patients with SM, use of peripheral blood stem cells (PBSC) was associated with higher odds for NE at day 21 compared with BM. The same effect on day 28 PE was observed only in patients who received PBSC with cell doses higher than 5.7 ×106 CD 34+ cells/kg. After adjusting for significant covariates, there were no differences in acute and chronic graft-versus-host disease (GVHD) or overall survival among the groups. However, recipients of mismatched grafts with SM had higher rates of chronic GVHD compared to patients with NS (RR 2.0, 95% CI 1.4–2.86, p<0.001). In conclusion, SM is associated with delayed engraftment while SP prior to HCT facilitates both neutrophil and platelet engraftment. However, spleen status at time of HCT had no significant impact on overall mortality or GVHD.
OR d21 WBC1 (95% CI2) p-value OR d28 Platelet3 (95% CI) p-value RR4 Overall Mortality (95% CI) p-value Normal spleen (NS) 1 - 1 - 1 - Splenectomy (SP) 2.25 (1.76–2.89) <0.01 1.28 (1.03–1.58) 0.03 1.01 (0.89–1.14) 0.85 Splenic irradiation (SI) 0.51 (0.40–0.66) <0.01 1.01 (0.78–1.31) 0.92 1.05 (0.90–1.22) 0.53 Splenomegaly (SM) 0.55 (0.48–0.63) <0.01 0.82 (0.72–0.93) <0.01 1.01 (0.93–1.09) 0.85 1 Odds ratio for day 21 neutrophil engraftment. 2 Confidence interval. 3 Odds ratio for d28 platelet engraftment. 4 Relative risk.

Disclosures:
Maziarz: Millenium: Speakers Bureau; Genzyme: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau.