CSF3R truncation mutations in a patient with B-cell acute lymphoblastic leukemia and a favorable response to chemotherapy plus dasatinib.

Activating mutations in the gene encoding for receptor of colony stimulating factor 3 (CSF3R) are drivers of pathogenesis in chronic neutrophilic leukemia (CNL) and atypical chronic myeloid leukemia (aCML). We describe a patient with newly diagnosed B-cell acute lymphoblastic leukemia (ALL) and three unique CSF3R truncating mutations which are predicted to be activating. After a slow early response to induction chemotherapy, dasatinib was added based on data from in vitro experiments demonstrating that dasatinib effectively targets key downstream kinases in CSF3R-mutated CNL/aCML. The patient subsequently achieved complete remission with minimal residual disease negativity that has been durable.