Higher cyclosporine-A concentration increases the risk of relapse in AML following allogeneic stem cell transplantation from unrelated donors using anti-thymocyte globulin.

Cyclosporine-A (CsA) is used to prevent acute graft-versus-host disease (aGvHD). European Society for Blood and Marrow transplantation (EBMT) recommends a CsA target serum concentration of 200-300 µg/L during the first month after allogeneic hematopoietic stem cell transplantation (HSCT). With this study, we investigated whether a median CsA concentration > 200 µg/L (CsAhigh) the first month after HSCT, compared to ≤ 200 µg/L (CsAlow), increased the relapse risk of acute myloid leukemia (AML), using unrelated donors (URD) and antithymocyte globulin (ATG). Data was collected from 157 patients with AML, transplanted 2010-2016. The cumulative incidence of relapse (CIR) at 60 months was 50% in the CsAhigh versus 32% in the CsAlow group (p = 0.016). In univariate analysis, CsAhigh versus CsAlow (p = 0.028), 10-unit increase of CsA as a continuous variable (p = 0.017) and high risk disease (p = 0.003) were associated with higher CIR. The results remained after adjusting for disease risk. Death following relapse occurred more frequently in the CsAhigh group (p = 0.0076). There were no significant differences in rates of aGvHD, chronic GvHD (cGvHD), EBV/CMV-infections or overall survival (OS) between the two groups. In conclusion, we found that a median CsA concentration > 200 µg/L, the first month after HSCT, results in higher CIR of AML when combined with ATG.