Addition of More Immunosuppressive Drugs As Graft-Versus-Host Disease (GVHD) Prophylaxis Does Not Improve Gvhd Outcomes in Reduced Intensity Allogeneic Hematopoietic Cell Transplantation from Unrelated Donors

Background: Reduced-intensity conditioning (RIC) regimens have led to a dramatic reduction of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The concept of RIC is to deliver adequate immunosuppression with manageable graft-versus-host disease (GVHD) and the eventual development of a potent graft-versus-leukemia effect. Nevertheless, GVHD prophylaxis remains a challenging task after allo-HSCT. While the combination of cyclosporine A (CsA) and a short course of methotrexate (Mtx) after transplantation is considered as the gold standard for GVHD prophylaxis after conventional myeloablative allo-HSCT from HLA-identical siblings, there is no consensus on the optimal preventive GVHD prophylaxis after RIC allo-HSCT. On the other hand, recent and ongoing studies are evaluating a promising GVHD prophylaxis strategy using post-transplantation cyclophosphamide (PTCy). The aim of this study is to evaluate the impact of different GVHD prophylaxis used after RIC allo-HSCT in patients receiving peripheral blood stem cells (PBSC) from unrelated donors for hematological malignancies. Patients and methods: We evaluated 127 consecutive patients with hematological malignancies who received RIC allo-HSCT and were followed in our center between January 2008 and January 2016; 74 (58%) were males, median age was 58 years (range: 18-70), 52 (41%) had acute myeloid leukemia, 36 (28%) myelodysplastic syndrome, 12 (10%) myeloproliferative syndrome, 9 (7%) Non-Hodgkin lymphoma, 9 (7%) chronic lymphocytic leukemia, 6 (5%) multiple myeloma and 3 (2%) chronic myeloid leukemia. At transplantation, 65 (51%) patients were in complete response (CR) or chronic phase (CP). RIC regimen consisted on fludarabine, intermediate doses of IV busulfan and anti-thymocyte golbulins (ATG) (Thymoblobulin) in 56 (44%) patients and a sequential FLAMSA regimen in 71 (56%) patients and who also received similar doses of ATG (Thymoglobulin). PBSC donors were 10/10 HLA matched in 81 (64%) patients and 9/10 HLA mismatched in 46 (36%) patients. Patients were divided according to GVHD prophylaxis into 3 groups: group 1 consisted on CsA alone with 23 (18%) patients, group 2 include patients who received either CsA + mycophenolate mofetil (MMF), n= 64 (50%) or CsA + Mtx, n= 20 (16%) or CsA + cyclophosphamide n= 5 (4%), and group 3 included patients receiving CsA + MMF + tacrolimus n= 15 (12%) patients. Results: After transplantation, all patients in group 1 engrafted after a median of 17 (3-25) days, 81/89 (91%) engrafted in group 2 after a median of 17 (5-58) days and 14/15 (94%) engrafted in group 3 after a median of 16 (9-24) days. We did not observe any significant impact of the type of GVHD prophylaxis on the 100-day incidence of grade II to IV acute GVHD, which occurred in 6/15 (40%), 34/81 (42%) and 7/14 (50%) for the groups 1, 2 and 3 respectively (p=0.18). Grade III-IV acute GVHD occurred in 3 (20%), 24 (29%) and 5 (33%) in the three groups respectively (p=0.11). Similarly, cumulative incidence of 1 year chronic GVHD was not different between groups 1, 2 and 3 reaching 46%, 43% and 46% respectively (p=0.6) among them 3/15 (20%), 18 (22%) and 3/14 (21%) patients had an extensive form. After a median follow-up of 22 months for surviving patients, although there was no significant difference between the three groups in terms of non-relapse mortality, we observed more infection-related mortality with 45% and 83% in groups 2 and 3 respectively compared to 47% in group 1. The cumulative incidence of relapse at 2 years was 22%, 31 and 26% for the three groups respectively (p=0.23). Overall survival rates at two years were 43%, 31% and 44 % for groups 1, 2 and 3 respectively (p=0.42). The multivariate analysis taking into account the type of disease, donor HLA matching, disease status at transplantation, type of RIC and the type of prophylaxis, showed that the incidence of acute GVHD was influenced only by the use of FLAMSA regimen from mismatched donors, HR= 2.2 [1.3-3.1], p=0.05 which had also the same impact on the occurrence of chronic GVHD. Conclusion: Despite its limitations and the need for prospective randomized studies, the results of our study suggest that in the RIC allo-HSCT from unrelated donors, the different GVHD prophylaxis associations lead to similar GVHD outcomes. Patients with more immunosuppressive drugs had a higher incidence of infection-related mortality and in which PTCy could be a better option. Disclosures Nicolini: BMS: Consultancy, Honoraria; Novartis: Honoraria, Membership on an entity9s Board of Directors or advisory committees, Research Funding; Ariad: Honoraria, Membership on an entity9s Board of Directors or advisory committees.