Abstract: BACKGROUND: The regimen of cyclosporin combined with four times of short-range methotrexate is still recognized as the classic prevention regimen for acute graft-versus-host disease. Previous studies have shown that whether day 11 methotrexate is used in sibling transplantation has no effect on the incidence of acute graft-versus-host disease. However, the effect of reducing day 11 methotrexate on the incidence of acute graft-versus-host disease in haploid hematopoietic stem cell transplantation patients remains unclear. 
OBJECTIVE: To investigate the efficacy of the omission of day 11 methotrexate in the regimen for the prophylaxis of graft-versus-host disease in haploid hematopoietic stem cell transplantation.  
METHODS: The clinical data of 63 patients with malignant hematologic diseases who received haploid hematopoietic stem cell transplantation from January 2017 to December 2019 were retrospectively analyzed. The graft-versus-host disease prevention regimen was cyclosporine combined with methotrexate 15 mg/m2 on day 1, 10 mg/m2 on day 3, day 6 and day 11. In the observation group (n=19), oral mucositis was grade III-IV at day 11, and day 11 methotrexate was cancelled. In the control group (n=44), oral mucositis was grade 0-II at day 11, and day 11 methotrexate was applied. The implantation situation, incidence of acute graft-versus-host disease, overall survival rate, and recurrence rate of the two groups were analyzed.   
RESULTS AND CONCLUSION: (1) The median follow-up time was 30(3-54) months and all neutrophils were successfully implanted in both groups. The median implantation time was 12(9-29) days and 12(8-25) days, respectively, showing no significant difference (P=0.682). There was one patient with poor platelet implantation in the observation group, and four patients with poor platelet implantation in the control group. The median time of platelet implantation was 12(9-18) days and 13(9-31) days in the two groups, respectively, (P=0.71), showing no statistical difference. (2) The overall incidence of acute graft-versus-host disease was 44.4%, and grade II-IV acute graft-versus-host disease was 28.6%. The incidence of II-IV acute graft-versus-host disease in the observation group and control group was 31.5% and 27.3%, respectively, (P=0.728), and there was no statistical difference between the two groups. (3) The results showed that for haploid hematopoietic stem cell transplantation, the omission of day 11 methotrexate did not increase the incidence of acute graft-versus-host disease compared with the standard methotrexate regimen. 

Key words: hematological malignancy, methotrexate, cyclosporine, graft-versus-host disease, oral mucositis