Comparing de novo chronic myeloid leukemia in blastic phase with Philadelphia chromosome-positive acute lymphoblastic leukemia after allogeneic hematopoietic cell transplantation.

Background: De novo chronic myeloid leukemia in blastic phase (CML-BP) showing lymphoid immunophenotype mimics Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph-positive ALL). Although upfront allogeneic hematopoietic cell transplantation (HCT) is considered in both diseases, it is not yet clear whether the transplant outcomes are also similar.

Methods: Using a registry database, the transplant outcomes between de novo CML-BP and Ph-positive ALL in negative-minimal residual disease (MRD), positive MRD, and nonremission cohorts were compared, respectively. All of the included patients had received tyrosine kinase inhibitor therapy before HCT and underwent HCT between 2002 and 2021. Regarding Ph-positive ALL, patients with p210 transcripts were excluded because there was concern that this group might include patients with de novo CML-BP.

Results: Although most of the outcomes were comparable, in patients with positive MRD at HCT, de novo CML-BP was significantly associated with superior disease-free survival (DFS) (hazard ratio [HR] 0.6, p = .0032), overall survival (HR 0.66, p = .027), and a lower risk of relapse (HR 0.48, p = .0051). In subgroup analyses, BCR::ABL1 mutation status had a significant interaction with the disease (p for interaction = .0027). De novo CML-BP seemed to be associated with superior disease-free survival in a BCR::ABL1 mutation-positive cohort, whereas this association was not observed in a mutation-negative cohort.

Conclusions: Considering previous reports that showed inferior outcomes for de novo CML-BP compared to Ph-positive ALL, the data suggested that allogeneic HCT could overcome the poor prognosis of de novo CML-BP. These findings highlight the importance of distinguishing de novo CML-BP from Ph-positive ALL.