LAUSR

Background A combination of calcineurin inhibitor and methotrexate (MTX) is one of a standard GVHD prophylaxis in allogeneic hematopoietic stem cell transplantation. However, MTX delays engraftment particularly in cord blood transplantation (CBT). Methods We conducted a retrospective study to evaluate an efficacy of mini-dose of MTX as a GVHD prophylaxis in single unit CBT. We compared the clinical outcome of patients with hematological malignancies in our institution who received standard-dose MTX (St-MTX, 15 mg/m2 of MTX on day 1 and 10 mg/m2 on days 3 and 6) as a GVHD prophylaxis in CBT between 2004 and 2013 and those who received mini-dose MTX (Mini-MTX, 5 mg/m2 of MTX on days 1, 3 and 6) between 2013 and 2018. Results Thirty-two patients received St-MTX and 26 patients received Mini-MTX. There was no statistically significant difference between 2 groups except for patients’ age (St-MTX; 46.5 years, Mini-MTX; 55.0 years, P = 0.0215). Cumulative incidence of neutrophil engraftment was significantly higher in Mini-MTX group (St-MTX; 71.9 %, Mini-MTX; 96.2 %, P = 0.0157). Cumulative incidence of grade II to IV and grade III to IV of acute graft-versus-host disease (GVHD) were 34.4 % and 6.2 % in St-MTX group, and 34.6 % and 7.7 % in Mini-MTX group with no statistical significance. Day 180 non-relapse mortality (NRM) rate was significantly lower in Mini-MTX group compared to St-MTX group (25.0 % vs 3.8 %, P = 0.0279), whereas relapse rate was almost equivalent between these groups. Multivariate analysis also indicated that Mini-MTX significantly improved engraftment (HR, 0.1368; 95% CI, 0.01902 to 0.9841; P = 0.048), and reduced the risk of NRM (HR, 0.1234; 95% CI, 0.01624 to 0.9380; P = 0.043). Day 180 OS were 71.9 % in St-MTX group, and 88.5 % in Mini-MTX group (P = 0.121), and PFS were 62.5 % in St-MTX group, and 80.8 % in Mini-MTX group (P = 0.136). Conclusion Our study suggests that GVHD prophylaxis using mini-dose MTX is feasible and associated with improvement of engraftment and decrease of transplant-related complication early after CBT.