Overcoming minimal residual disease using intensified conditioning with medium-dose etoposide, cyclophosphamide and total body irradiation in allogeneic stem cell transplantation for Philadelphia chromosome-positive acute lymphoblastic leukemia in adults

Intensified conditioning regimens with total marrow irradiation/etoposide/cyclophosphamide and busulfan/etoposide/cyclophosphamide overcome the impact of pre-transplant minimal residual disease on outcomes in high-risk acute lymphoblastic leukemia patients in complete remission

PURPOSE

Among high-risk acute lymphoblastic leukemia (ALL) patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT), those with positive minimal residual disease (MRD) are susceptible to poor outcomes. Therefore, it is necessary to determine the most suitable preparatory regimen for these patients.

METHODS

Data were analyzed from 141 patients who received allo-HSCT and were diagnosed with high-risk ALL. These patients underwent intensified conditioning regimens, including either total marrow and lymphoid irradiation (TMLI)-etoposide (VP16)-cyclophosphamide (CY) or busulfan (BU)-VP16-CY between October 2016 and November 2022. A total of 141 individuals were in complete remission (CR) before transplantation and, among all patients, 90 individuals exhibited a negative MRD status and 51 patients had a positive MRD status.

RESULTS

In patients who tested negative for MRD, the incidence of relapse within a 2-year timeframe was 25.0% (24.8%-25.5%), compared with 32.2% (31.2%-33.2%) in MRD-positive patients; however, this difference was not statistically significant. There were no significant differences in the 2-year disease-free survival (DFS) and 2-year overall survival (OS) rates between the MRD-negative and MRD-positive groups (DFS: 67.2% (57.9%-78.1%) vs. 55.5% (42.6%-72.3%); OS: 69.0% (61.9%-88.2%) vs. 66.7% (53.9%-82.5%)). Furthermore, no notable variations were observed in the occurrence of transplant-related mortality (TRM) and graft-versus-host disease (GVHD) across the two groups.

CONCLUSION

This study reveals the benefits of TMLI-VP16-CY and BU-VP16-CY conditioning regimens in high-risk ALL patients with CR and MRD-positive status. A large-scale prospective clinical trial is warranted in the future.

Medium-dose etoposide, cyclophosphamide and total body irradiation conditioning potentiates anti-leukemia immunity in adults with acute lymphoblastic leukemia without aggravating graft-versus-host disease

Medium-dose etoposide (ETP), cyclophosphamide (CY) and total body irradiation (TBI) is a beneficial conditioning regimen for allogeneic hematopoietic cell transplantation (allo-HCT) in adults with acute lymphoblastic leukemia (ALL), especially with high-risk ALL, as compared with CY and TBI conditioning. ETP may enhance immunogenicity of leukemia-associated antigens through increased expression of major histocompatibility antigen complex class I, leading to cross-priming of T cells by dendritic cells and generating leukemia-specific cytotoxic T cells. Furthermore, ETP can eliminate activated effector T cells, sparing naïve and memory T cells, accompanied with depletion of regulatory T cells. These mechanisms are supposed to lead to inhibit immune escape of leukemia cells and enhance anti-leukemia immunity in addition to direct cytotoxicity of ETP, followed by an efficient eradication of leukemia cells. According to the findings of pharmacokinetics studies, spreading the administration of low-dose ETP may be more efficacious than non-spreading administration, to induce a potent anti-leukemia immunity without aggravating graft-versus-host disease and transplant-related toxicity. In the present review, I discuss the immunological aspects elicited by the addition of medium-dose ETP to the CY/TBI conditioning and the possible positioning of allo-HCT with this conditioning in adults with ALL, considering recent progress in non-HCT treatment including bispecific antibody-based therapy.