IFN-α Is Effective for Treatment of Minimal Residual Disease in Patients with Acute Leukemia after Allogeneic Hematopoietic Stem Cell Transplantation: Results of a Registry Study

- MRD after allo-HSCT is associated with relapse.
- We examined the efficacy of MRD-directed IFN-α in a registry study.
- The 2-year cumulative incidence of relapse and NRM was 11.5% and 4.3%, respectively.
- The 2-year probabilities of EFS and DFS were 66.5% and 82.4%, respectively.
- MRD-directed IFN-α treatment is effective for patients after allo-HSCT.

The efficacy of minimal residual disease (MRD)-directed IFN-α treatment was investigated in acute leukemia patients who were positive for MRD after allogeneic hematopoietic stem cell transplantation (allo-HSCT) (n = 107). MRD-positive status was defined as positivity for leukemia-associated aberrant immune phenotypes or positivity for Wilms' tumor gene 1 in a single bone marrow sample. Recombinant human IFN-α-2b injections were administered subcutaneously 2 to 3 times per week for 6 months. The 2-year cumulative incidence of severe acute and chronic graft-versus-host disease after IFN-α treatment was 5.7% and 6.6%, respectively. Eighty-one patients (75.7%) turned MRD-negative after IFN-α treatment 1 month (42; 39.3%), 2 months (6; 5.6%), 3 months (7; 6.5%), and >3 months (26; 24.3%) after MRD-directed IFN-α treatment. Twelve patients showed relapse after IFN-α treatment, and 7 died of relapse. Four patients died of nonrelapse mortality (NRM). The 2-year cumulative incidence of relapse, relapse mortality, and NRM after IFN-α treatment was 11.5%, 6.8%, and 4.3%, respectively. The 2-year probabilities of event-free survival, disease-free survival, and overall survival after IFN-α treatment were 66.5%, 82.4%, and 87.4%, respectively. Persistent MRD after IFN-α treatment was significantly associated with higher relapse risk and poorer survival. Thus, MRD-directed IFN-α treatment is effective for patients who were MRD-positive after allo-HSCT. The study was registered at http://clinicaltrials.gov as NCT02185261.