Disease overview: Chronic myelomonocytic leukemia (CMML) is a clonal hematopoietic stem cell disorder that is classified as a myelodysplastic/myeloproliferative neoplasm by the 2008 World Health Organization classification of hematopoietic tumors. It is characterized by absolute monocytosis (>1 × 10⁹/L) in the peripheral blood that persists for at least 3 months.
Diagnosis: The diagnosis of CMML rests on a combination of morphologic, histopathologic and chromosomal abnormalities in the bone marrow. It is important to exclude other myeloproliferative neoplasms and infectious/autoimmune conditions that can cause monocytosis.
Risk stratification: Several CMML-specific prognostic models incorporating novel mutations have been recently reported. The Mayo prognostic model classified CMML patients into three risk groups based on: increased absolute monocyte count, presence of circulating blasts, hemoglobin <10 gm/dL and platelets <100 × 10⁹/L. The median survival was 32 months, 18.5 months and 10 months in the low, intermediate, and high-risk groups, respectively. The Groupe Francophone des (GFM) score segregated CMML patients into three risk groups based on: age >65 years, WBC >15 × 10⁹/L, anemia, platelets <100 × 10⁹/L, and ASXL1 mutation status. After a median follow-up of 2.5 years, survival ranged from not reached in the low-risk group to 14.4 months in the high-risk group.
Risk-adapted therapy: The Food and Drug Administration has approved azacitidine and decitabine for the treatment of patients with CMML. An allogeneic stem cell transplant can potentially offer a curative option to a subset of CMML patients. It is hoped that with the discovery of several novel mutations, targeted therapies will become available in the near future.
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