Chronic Myelomonocytic Leukemia

This chapter discusses chronic myelomonocytic leukemia (CMML), a clonal hematopoietic stem cell disorder with overlapping features of myelodysplastic syndromes (MDS) and myeloproliferative neoplasms. The incidence of CMML has been approximated at 12.8 cases per 100,000 people per year, with the median age of presentation being 65-75 years. Cytogenetic abnormalities in CMML can be detected by conventional karyotyping or fluorescent in situ hybridization (FISH) studies. The treatment for CMML can be broadly divided into two categories: supportive care and directed or targeted therapy. Supportive care focuses on symptom management and palliation, and it comes into play when patients are ineligible for, or have failed, directed therapy. For directed or targeted therapy, the hypomethylating agents 5-azacitidine and decitabine have been approved by the US Food and Drug Administration for MDS. These agents have been used in CMML with varying success, and allogeneic stem cell transplantation remains the only curative option for patients with CMML. This technique is, however, fraught with complications, such as graft rejection, nonrelapse mortality (NRM), acute and chronic graft-versus-host disease (GVHD), organ injury, and disease relapse in the posttransplant period.