The Comparison of Myeloablative Versus Reduced Intensity Conditioning Regimen in ABO Mismatched Allogeneic Hematopoietic Cell Transplantation.
Authors: Topcuoglu Pervin , Arat Mutlu , Bolukbasi Tugce , Soydan Ender , Ozer Yesim , Ozcan Muhit , Gurman Gunhan , Demirer Taner , Akan Hamdi , Beksac Meral , Arslan Onder , Ilhan Osman 
Published: April 2020

Abstract
Recently, in an effort to reduce the transplant related mortality, AHCT with reduced intensity conditioning (RIC) have been developed. It has been reported that patients receiving RIC from an ABO-mismatched donor had more transplant-associated complications compared to ablative AHCT (BMT2001;28: 315, Transfusion2002; 42:1293, Transfusion2003; 43: 1153). In this single center, retrospective, historical case-matched study, we aimed to analyze the influence of ABO-incompatibility on transplant-related morbidity and mortality between ablative and RIC. Between 1988 and 2003, 39 patients underwent AHCT with RIC and only 14 were ABO-incompatible. Ten patients with ABO-incompatibility and having a regular follow-up for blood group typing were evaluated for immuno-hematological complications, such as acute or delayed-type hemolysis (DTH), pure red cell aplasia (PRCA), thrombotic thrombocytopenic purpura (TTP) and early transplant-related complications, were compared to 20 case control recipients having matched pretransplant characteristics and similar follow up, but myeloablative regimen, either bone marrow (BM) or peripheral blood (PB) stem cells infused. Patients’ characteristics are shown in table below. All the recipients and donors underwent a detailed pretransplant work up and all the recipients were followed twice a week post transplant by a transfusion specialist according to guidelines (BMT, 2001;28:315). Median follow-up was 195 days (range, 51–538d). We did not observe any acute hemolysis, but 11 experienced DTH. No significant differences were encountered among the three groups in terms of DTH (p=0.356). In all recipients having a major ABO incompatibility, the blood group switched to donor type, but 50% of the patients with minor ABO-incompatibility still had either their antigen persistency or the appearance of donor-derived isoagglutinins. We observed mild (n=1, BM group) and severe pure red cell aplasia (n=1, RIC group) in two patients having a major ABO-incompatibility. TTP was developed in one patient with major ABO-incompatibility. In conclusion, we did not observe any difference between ablative AHCT and RIST in ABO incompatible patients in terms of immuno hematological complications in contrast to published case series. In addition, we could not show any negative impact of ABO-incompatibility on the severity of acute GVHD and the rate of early transplant related mortality.
Table
Conditioning Ablative Reduced Intensity Source (patients) PB (n=10) BM (n=10) PB (n=10) Gender (M/F) 2/8 6/4 5/5 Median age (range) 34 (16–45) 31 (17–46) 33 (21–47) Diagnosis CML (2), AML (7), other (1) CML (2), AML (6), other (2) CML (4), AML (1), other (5) ABO-incompatibility Major 5 6 5 Minor 5 4 5 Delayed type hemolysis 5 (50%) (22,23,55,90,120) 2 (20%) (18,27) 4 (40%)(20,130,165,188) RBC transfusion (100 days) 3 (0–15) 4 (0–10) 5 (0–10) Median days of the independence from pRBC 7 (0–31) 18 (0–41) 7 (0–28) Median follow-up (days) 195 (90–538) 194 (63–467) 200 (51–511) Acute GVHD (grade II–IV) n (%) 3 (30%) 4 (40%) 4 (40%) TRM 100, n (%) 1 (%10) 1 (%10) 1 (%10)