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Post-transplantation cyclophosphamide (PTCy) can reduce the incidence of graft versus host disease (GVHD) and this intervention is often applied on adults with hematologic malignancy. However, the high relapse rate hinders the development of the intervention and data of PTCy used on children with hematologic malignancy remains limited. In order to overcome issue of high relapse rate in PTCy treatment, we used fludarabine (Flu), enhanced dose of cytarabine (Ara-C, 9 g/m2), busulfan (Bu), Cy, anti-thymocyte globulin (ATG) combined with PTCy for an intensified conditioning regimen. A total of 22 children with acute leukemia received intensified PTCy conditioning regimen (PTCy intensified group). We matched with 18 children who received modified Bu-Cy and ATG conditioning regimen in the same period (ATG group). The two-year cumulative incidences of grade II–IV acute GVHD was significantly lower in PTCy intensified group (13.6 ± 7.7% vs 38.9 ± 11.5%, P = 0.048). Two-year GVHD-free relapse free survival (GRFS) in PTCy seems to be better among the increment group despite not being significant (63.3 ± 10.3% vs 35.4 ± 11.9%, P = 0.092). The positive rate of minimal residual disease after transplantation was significantly lower than that before transplantation (20.0% vs 2.5%, P = 0.029). In conclusion, ATG and PTCy combined with Flu-based increased intensity conditioning regimen is effective for acute leukemia in children. It could reduce GVHD rate significantly and potentially improve GRFS. [ABSTRACT FROM AUTHOR]

Relapse and graft-versus-host disease (GVHD) are the important complications influencing mortality for patients with high-risk acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS) after allogeneic hematopoietic stem cell transplantation (allo-HSCT). GVHD prophylaxis based on post-transplant cyclophosphamide (PTCy) or antithymocyte globulin (ATG) is widely used in haploidentical HSCT (haplo-HSCT). We developed a modified intensified conditioning regimen including fludarabine (Flu) and investigated the effect of ATG-PTCy combination on transplant outcomes in high-risk AML and MDS compared with those patients who received only ATG as GVHD prophylaxis. A total of 80 patients with high-risk AML and MDS were divided into two groups and assigned to one-to-one pairing. The modified ATG-PTCy group had more infused mononuclear cells, CD34-positive cells and CD3-positive cells than those in the ATG group (P < 0.05). The amount of platelet transfusion was higher in the ATG group than the modified ATG-PTCy group [2 (range, 1–6) U vs 2 (range, 1–5) U, P = 0.005]. The median of platelet recovery was better in the modified ATG-PTCy group than in the ATG group (12 days vs 13 days, P = 0.041). The infection rates of bacteria, fungi and virus at 100 days after transplantation were similar in both groups. Compared with the ATG group, individuals who received the modified ATG-PTCy regimen had higher 2-year GVHD- and relapse-free survival(GRFS) [60.0% (95%CI, 44.9–75.1%) vs 34.8% (95%CI, 19.9–49.7%), P = 0.028]; lower 180-day incidence of II-IV acute GVHD (aGVHD) [15.0% (95%CI, 4.0–26.0%) vs 39.8% (95%CI, 23.9–55.7%), P = 0.029]; lower 1-year incidence of moderate to severe chronic GVHD (cGVHD) [2.9% (95%CI, 2.0–3.8%) vs 19.6% (95%CI, 5.3–33.9%), P = 0.039]; and without an increase in the 2-year cumulative incidence of relapse (CIR) [19.5% (95%CI, 6.6–32.4%) vs 30.4% (95%CI, 15.3–45.5%), P = 0.291]. High-dose stem cells can promote blood cell implantation. The modified ATG-PTCy combination was associated with decreased risk of aGVHD and cGVHD, no increased risk of recurrence, and improved GRFS. It represents an effective strategy for high risk AML and MDS. [ABSTRACT FROM AUTHOR]