Chronic Myelomonocytic Leukemia 10 Years of Single Institute Experience

Introduction

Chronic myelomonocytic leukemia (CMML) is a rare de novo clonal hematopoietic stem cell disorder with overlapping features of myeloproliferative neoplasms (MPN) myelodysplastic syndromes (MDS). The median age at CMML diagnosis is around 71‐73 years, with a male being more affected. According to the 2022 World Health Organization (WHO) classification of myeloid neoplasms, CMML is characterized by the presence of sustained (>3 months) peripheral blood (PB) monocytosis (≥1 × 109/L; monocytes ≥10% of white blood cell count) along with dysplastic features in the bone marrow (BM). < 20% blasts/blasts equivalent in the PB and BM. CMML categorized into “proliferative” (MPN‐CMML) and “dysplastic” (MDS‐CMML) sub‐types; based on a total leukocytic count (TLC) (of ≥13 × 109/L for MPN‐CMML). Also, based on PB and BM blast %, CMML can be also sub‐classified into three categories; (a) CMML‐0 (<2% PB blasts including promonocytes and <5% BM blasts), (b) CMML‐1 (2‐4% PB blasts including promonocytes and 5%‐9% BM blasts), and (c) CMML‐2 (>5% PB blasts including promonocytes and 10%‐19% BM blasts and/or when any Auer rods are present.

Materials and methods

To retrospectively analyze the cases of CMML diagnosed in the Hematology Department, National Center for Cancer Care and Research (NCCCR), Doha, Qatar from January 2013 to June 2024 with the assessment of risk and prognosis. We assessed general characteristics, peripheral blood, bone marrow , cytogenetic and molecular finding in our patients .Mayo Clinic and CSSP calculated for risk stratification.

Results

A sum of twenty-one patients with chronic Myelomonocytic Leukemia (CMML) were diagnosed at our center. The majority of all CMML cases were males12/21(81%), with mean age 56 range (25-87) and 5 patients were less than 40 years old. Majority of the patients were from Asian background 14 (68%). The initial laboratory investigations at diagnosis were mean HB 9.1 g/dl, WBC 22.8x10^3/uL, ANC 11.2x10^3/uL, AMC 6.5x10^3/uL, Basophils1.8x10^3/uL, Eosinophils 0.8x10^3/uL, Platelet 87.9x10^3/uL, LDH 385.2 mmol/, Blast percentage was 0.1% on peripheral blood and 1.7% on bone marrow. On examination, a total of 7/21 (33%) found to have splenomegaly. More than 50% of the patients established proliferative CMML subtype (57%) by bone marrow examination. None out of the thirteen-bone marrow sample in which JAK2 mutation was performed was detected, on the other hand an extra copy of BCR-ABL was detected in one sample. In these patients the diploid KT was most common cytogenetic findings 52%, while complex and monosomy 7 were 9% each. The most common mutations detected were DNMT3A, NPM1, NRAS with 14% each. The prognostic outcome was calculated by two different scales, CMML Mayo Clinic and CSSP scale. The Mayo Clinic scale demonstrates 53% high risk 3, 29% high risk 2 and 19% intermediate1, while 44% had high Score by CPSS. Hydroxyurea was used in 38% of the patients, azacytidine 24%, and 28% didn't utilize any treatment. fourteen patients required blood transfusion on regular basis. 70% are alive (46% with confirmed follow up ) and 30% passed away, of which two progressed to acute myeloid leukemia.

Conclusion

In our center for over 10 years period, CMML was confirmed only in 21 patients since it's a rare disease. The median age of our patients is much less than the international median, and more than 25% of them were adolescence and young adult (AYA ) less than 40 years. However males still predominated same as other centers. Proliferative sub type, high risk more common. More prospective studies and clinical trials are needed in the future with more usage of the new prognostic scores including mutation and new treatment strategies like add BCL2 inhibitors to look at the outcome specially in centers like ours with younger patients.

No relevant conflicts of interest to declare.