Platelet and Red Blood Cell (RBC) Transfusion Requirements of Nonmyeloablative (NM) HLA-Matched Related and Unrelated Donor Hematopoietic Cell Transplantation (HCT): Influence of Genetic Disparity and ABO-Incompatibility.

NM-HCT makes use of graft-versus-tumor effects and has been applied to treat pts with hematological malignancies who were ineligible for conventional myeloablative (M)-HCT. The current study retrospectively analyzed platelet and RBC transfusion requirements within the first 100 days after HCT in 365 consecutive pts given NM- HCT from HLA-matched related (MRD; n=187) or unrelated donors (URD; n=178) between December 1997 and January 2005. Diagnoses included NHL and HD (29.5%), MM (19.4%), acute leukemias (20%), chronic leukemias (14.8%) and others (16.3%). Pts’ age ranged from 9 months to 74.5 (median 50.1) years. We also asked whether ABO incompatibility increased transfusion requirements in NM recipients, and whether there were differences in transfusion requirements between related and unrelated recipients within the subgroup of ABO-mismatched recipients. Further, overall transfusion requirements were compared to those among 1430 concurrent HLA-matched recipients given M-HCT. Among NM recipients, a higher percentage of unrelated recipients required transfusions than of related recipients (48% vs.25% for platelets p<0.0001, and 87% vs.68% for RBC p<0.0001). Unrelated recipients were also given more daily platelet and RBC transfusion units compared to related recipients (p<0.0001). Major and bi-directional ABO-mismatched recipients had increased requirements for both platelet and RBC transfusions compared to either ABO-matched or minor ABO-mismatched recipients (p=0.0394 and 0.0009 for platelets and RBC, respectively). Within the ABO-mismatched subpopulation, a higher percentage of unrelated recipients received transfusions, and had greater number of daily RBC transfusion requirements compared with related recipients (median of 0.09 versus 0.04, respectively; p=0.039), while platelet transfusion requirements were comparable. Finally, 36% and 77% of NM recipients respectively received platelet and RBC transfusions, compared to 99% and 94% of M recipients respectively (p<0.0001). In conclusion, our data showed that the NM regimen reduced the requirements for platelet and RBC transfusions compared to M regimens. ABO-incompatibility between donors and recipients adversely affected transfusion requirements. Unrelated recipients experienced more profound pancytopenias, possibly owing to greater non-HLA disparities, resulting in greater transfusion requirements.