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CMML is classified as a myelodysplastic/myeloproliferative neoplasm (2008, WHO). Compared with other haematological malignancies it is an uncommon disorder, and there are few large studies regarding outcome. Approximately 9.5% of patients registered with the Irish National Registry for Myelodysplastic Syndromes (MDS) between 2007 and 2014 had CMML.

We evaluated presenting symptoms, diagnostic findings, cytogenetics and treatment received including blood transfusions, haematopoietic growth factors, hypomethylating agents, chemotherapy and transplantation.

The median age at diagnosis was 75 years (range 56 - 89) with male: female ratio of 1.9:1.  Nineteen patients (65.5%) were asymptomatic at presentation and 10(34.5%) had constitutional symptoms, bleeding, and/or splenomegaly. Apart from monocytosis in all patients, features at presentation included anaemia (65.5%), thrombocytopenia (55%), leukocytosis (45%), neutropenia (20.5%), raised LDH (68.9%) and splenomegaly (17%). Peripheral blasts were present in 5 patients, all of whom subsequently developed Acute Myeloid Leukaemia (AML).  JAK2V617F mutation was negative in all patients tested (n=9). Seven patients (44%) had CMML-2 and 21(72.4%) CMML-1. Ninety three percent of patients had a hypercellular marrow. Evidence of dysplasia (93% dyserythropoiesis, 86% myeloid dysplasia, 72% megakaryocytic dysplasia) and increased reticulin fibrosis (73%) were noted. Only 7 patients (24.1%) had cytogenetic abnormalities, including trisomy 8 (n=2), t(8;21) (n=1), Monosomy 7 (n=1), trisomy 19 (n=2) and –Y (n=2). Seventeen patients (58.6%) received active management including Azacitidine (n=11), intensive AML-type induction therapy (n=2), allogeneic marrow transplant (n=1) and Hydroxycarbamide (n=6). Seven (24.1%) patients received transfusion support only. Erythropoietin was given in 7 patients (24.1%) and G-CSF in 2.  Sixteen patients (55%) required transfusion at diagnosis. Twelve patients (72%) required red cells and 13(68%) required platelets during the course of illness. Eight of 11 patients treated with Azacitidine remained transfusion dependent. Median survival was 20 months (0-154 months). Transformation to AML was seen in 7 patients (24.1%). Survival for patients who received Azacitidine was 22 months (11 to 154) with a median treatment cycles of 18 (3-33). One patient has been on Azacitidine for 7 years and remains alive 13 years after diagnosis. Median survival of patients who received Hydroxycarbamide and AML-type induction were 11.5 and 22 months respectively. Only one patient (with monosomy 7) received allogeneic transplantation but died 12 months later due to AML. Survival was 32 and 15 months respectively for patients with normal/ good risk karyotype and those with adverse cytogenetics and 18 months and 21 months respectively for those who received active management and those managed by best supportive care.

A significant number of CMML patients are diagnosed incidentally and the majority of patients are asymptomatic at diagnosis. The classical finding of splenomegaly is not always present. All male patients were anaemic at diagnosis. Adverse risk cytogenetics was less frequently encountered but indicated poor outcomes. Most patients were transfusion dependent and two thirds of patients were managed actively, mainly with Azacitidine.