Refined medullary blast and white blood cell count based classification of chronic myelomonocytic leukemias

Since 2001, chronic myelomonocytic leukemia (CMML) is classified by the WHO as myeloproliferative/myelodysplastic neoplasm. Herein we tried to better describe CMML patients with regard to hematological characteristics and prognosis using data of the Duesseldorf registry. We created 6 CMML subgroups, by dividing dysplastic and proliferative CMML at the cut-off of white blood cell count of 13,000/μL and splitting these two groups into 3 subgroups: CMML 0 with <5% blasts (n = 101), CMML I with 5-9% blasts (n = 204) and CMML II with 10-19% blasts (n = 81). For comparison we included patients with RCMD, RAEB I and II. The newly created CMML 0 group had better prognosis than CMML I and II, median survival times were 31 months (ms), 19 ms and 13 ms, respectively (p < 0.001). Median survival times between the corresponding dysplastic and proliferative subgroups 0 and 1 differed significantly: CMML 0 dysplastic 48 ms and CMML 0 proliferative 17 ms (p = 0.03), CMML I dysplastic 29 ms and CMML I proliferative 15 ms (p = 0.008), CMML II dysplastic 17 ms and CMML II proliferative 10 ms (p = 0.09). Outcome of CMML patients worsens with increasing medullary blasts and when presenting as proliferative type. Therefore it is justified to separate CMML with <5% medullary blasts.