How do you choose chemotherapy for a pediatric patient with mixed-phenotype acute leukemia?
I would begin treatment with a high risk ALL regimen and monitor response closely. While there is not a standard regimen for the treatment of MPAL, in several retrospective analyses, rates of remission and outcomes have been shown to be superior with initial ALL vs. AML or hybrid (both ALL and AML) regimens, particularly in cases with CD19 positivity. An exception would be the rare cases in which an AML-specific gene fusion is present and for these cases, I would use AML therapy instead. In patients who achieve remission at the end of induction with ALL therapy, I would continue with a high risk ALL regimen. While the criteria for switching to myeloid therapy and/or pursuing HSCT are also varied, I would reserve this for patients who do not achieve an M1 (<5% blasts) marrow at the end of an ALL-based induction or those patients who remain MRD positive (at least 0.01%) at the end of an ALL-based consolidation regimen. This treatment approach is currently being studied prospectively in the COG AALL1732 trial (NCT03959085).
References: