Impact of transplant conditioning, NPM1 mutations, and measurable residual disease in FLT3-ITD acute myeloid leukemia.

We conducted a post-hoc analysis of data from BMT CTN 1506 (MORPHO), a randomized trial of gilteritinib versus placebo as post-transplantation maintenance for patients with FLT3-ITD-mutated acute myeloid leukemia (AML) undergoing allogeneic hematopoietic cell transplantation (HCT), focusing the interactions between conditioning regimen intensity, measurable residual disease (MRD), and NPM1 co-mutation status reported from diagnosis. Comparing FLT3-ITD MRD before and after conditioning, there was no difference between myeloablative conditioning (MAC) and reduced intensity conditioning (RIC) in eradication or reduction of FLT3-ITD MRD. For participants who were FLT3-ITD MRD-negative pre-HCT, there was no difference in the cumulative incidence of relapse during follow-up between those receiving MAC versus RIC. NPM1 co-mutation was associated with the largest magnitude of relapse-free survival benefit from post-HCT gilteritinib, and in these participants, post-HCT gilteritinib in the setting of RIC appeared to be as effective as MAC at preventing relapse. Only in participants who were NPM1 wild-type at diagnosis and were FLT3-ITD MRD-positive prior to HCT did MAC appear superior to RIC in preventing relapse. Our findings suggest that only a subset of patients with FLT3-ITD AML undergoing HCT may benefit from myeloablative conditioning, and that, much like AML therapy prior to HCT, the intensity of the HCT regimen should be adapted according to the molecular features of the disease. (NCT02997202).