Peri-transplant conundrums: optimizing maintenance therapy using MRD-directed approaches

Improved understanding of the molecular underpinnings of acute leukemia has led to advances in the detection of very low levels of leukemia-specific abnormalities, known as measurable residual disease (MRD). The limit of detection for modern next-generation sequencing and polymerase chain reaction-based assays is as low as 10-6, allowing for quantitative and longitudinal monitoring in both acute myeloid leukemia (AML) and acute lymphoblastic leukemia (ALL). In the period surrounding allogeneic hematopoietic cell transplantation (HCT), detectable MRD is clearly associated with poor outcomes, primarily due to an increased risk of morphologic relapse. In this review, we address the use of maintenance therapy for patients with acute leukemia, including those who are MRD-positive prior to and following HCT. Post-HCT azacitidine may have a role for MRD-positive AML. In AML with FLT3-internal tandem duplication mutation, post-HCT gilteritinib and sorafenib can be evidence-based strategies to target MRD. In ALL, blinatumomab is a powerful tool to eradicate MRD in patients with Philadelphia (Ph)-positive or Ph-negative ALL; tyrosine kinase inhibitors are indicated for post-HCT management of Ph+ ALL. Despite these advances, the optimal duration and type of intervention still remain unknown for many patients with acute leukemia who have peri-HCT MRD.