LAUSR

Background Our group previously reported a 16% incidence of HC after hematopoietic cell transplantation (HCT) involving mostly matched unrelated donors (85%) and ATG-containing regimens (80%) (Silva, Haematologica 2010). PT-Cy is an effective GVHD prophylaxis in haplo- or matched unrelated transplants. There is a paucity of information about the risk of HC in this setting. Objective To retrospectively assess the incidence and clinical factors associated with HC in alloHCT recipients receiving PTCy as GVHD prophylaxis. Methods A retrospective analysis of patients (pts.) who underwent HCT with PT-Cy at our center between 2012-2018 was performed. We stratified the study cohort (N=478) into HC (N=193, 40%) and Non-HC (N=285, 60%) to compare their characteristics and outcome. Association between HC and clinical variables was assessed using logistic regression modeling. Results Pt's age, HCT-CI, # prior therapies, disease type and status were not statistically different between the 2 groups. However, the HC group pts. were more likely to have received more intense conditioning (Busulfan/Fludarabine(BF) +/- Clofarabine, or Thio; F/Melphalan (FM) 140+/-Thio or TBI vs. FM 100+/-TBI) (p=0.018), had haplo-transplants (p=0.018), BM as graft (p=0.021), and tacrolimus+mycophenolate mofetil (MMF) (p=0.043). Delayed ANC engraftment (p=0.032) and time to achieve an absolute lymphocyte count >500 was noted in HC group (p=0.014). 54% of HC pts. had grade 2-4 cystitis and BK virus was isolated in 87% of cases. CMV viremia was higher in HC group compared to Non-HC group (p Conclusion Our study showed a 40% incidence of HC after HCT recipients receiving PT-Cy. The intensity of the conditioning regimen is an independent predictive factor for developing HC. A formal comparison to ATG-containing regimens is in progress.