Target Therapy for Extramedullary Relapse of FLT3-ITD Acute Myeloid Leukemia: Emerging Data from the Field

SIMPLE SUMMARY: Extramedullary presentation of acute myeloid leukemia is a rare event that can occur at diagnosis or at relapse, together or independent of bone marrow involvement. This event is usually unamenable to standard therapies. Due to the rarity of this disorder, most of the literature comprises small retrospective studies and case reports. The introduction in clinical practice of newly approved drugs for acute myeloid leukemia will pave the way for new treatment approaches for this rare disease. This report will present a review of acute myeloid leukemia with extramedullary manifestations responding to FLT3-directed target therapy. ABSTRACT: FMS-like tyrosine kinase 3 (FLT3) is a receptor tyrosine kinase family member. Mutations in FLT3, as well known, represent the most common genomic alteration in acute myeloid leukemia (AML), identified in approximately one-third of newly diagnosed adult patients. In recent years, this has represented an important therapeutic target. Drugs such as midostaurin, gilteritinib, and sorafenib, either alone in association with conventional chemotherapy, play a pivotal role in AML therapy with the mutated FLT3 gene. A current challenge lies in treating forms of AML with extramedullary localization. Here, we describe the general features of myeloid sarcoma and the ability of a targeted drug, i.e., gilteritinib, approved for relapsed or refractory disease, to induce remission of these extramedullary leukemic localizations in AML patients with FLT3 mutation, analyzing how in the literature, there is an important development of cases describing this promising potential for care.