Chronic myelomonocytic leukaemia (CMML) is a rare type of cancer that causes an overproduction of white blood cells (WBCs) in the blood and bone marrowsoft, spongy tissue found in bones that makes blood cells. More specifically, it causes an overproduction of monocytes, which is the largest type of WBC in the blood that can develop into either a macrophage (ingest and degrade dead cells, debris, tumour cells and/or foreign substances) or a dendritic cell (initiate and regular the adaptive immune response).
Blood is the bodily fluid of the circulatory system that provides nutrients and oxygen to our tissues, and helps to remove waste from our bodies. There are three primary types of blood cells produced in the inner, spongy portion of the bone (bone marrow) from stem cells (immature blood cells that develop into either red blood cells (RBCs), white blood cells (WBCs), or platelets). RBCs, or erythrocytes, are responsible for providing oxygen to the tissues in our body, as well as transporting carbon dioxide to the lungs to be exhaled. WBCs are responsible for fighting infection and disease in the body. Platelets are blood cells that play a major role in blood clotting (or coagulation), which is an important process that helps reduce blood loss after injury.
CMML is classified as a mix of myelodysplastic syndromes (MDS) and myeloproliferative syndromes (MPN), as it shares characteristics of both. For more information on MDS or MPN, please refer to the Rare Cancers Australia Myelodysplastic Syndrome (MDS) page or the Myeloproliferative Neoplasms (MPN) page.
CMML is slightly more common in males, and tends to be diagnosed over the age of 70. However, anyone can develop this disease.
Types of Chronic Myelomonocytic Leukaemia
There are two types of CMML, which are characterised by the percentage of immature WBCs found in the blood and bone marrow.
Type 1 Chronic Myelomonocytic Leukaemia
Type 1 CMML is characterised by having between 2-4% of blasts (immature WBCs) in the blood and/or between 5-9% of blasts in the bone marrow. This subtype is characterised by the absence of Auer rods, which are long, needle-like structures that are present in abnormal cells under the microscope. Type 1 is not as aggressive as type 2 CMML, and can have a better prognosisto predict how a disease/condition may progress and what the outcome might be than those with type 2 CMML.
Type 2 Chronic Myelomonocytic Leukaemia
Type 2 CMML is characterised by having between 5-19% of blasts in the blood and/or between 10-19% of blasts present in the bone marrow. Some patients with this subtype also have Auer rods present within the cancer cells, which are often indicative of aggressive disease behaviour. Type 2 CMML tends to be more aggressive than type 1 CMML, and may not have as good of a prognosis.
Transformation into Acute Myeloid Leukaemia
In some cases, CMML that has been left untreated can develop into acute myeloid leukaemia (AML), which is a rare type of leukaemia that causes an overproduction of myeloid cells (a specific type of dendritic cell) in the blood. For more information on AML, please refer to the Rare Cancers Australia Acute Myeloid Leukaemia (AML) page.
Treatment
When cancers are detected, they are staged and graded based on size, metastasis, and how the cancer cells look under the microscope. Staging and grading helps your doctors determine the best treatment for you. However, because of how rare CMMLs are, there is currently no standard staging and grading system for this disease. Instead of staging and grading, your doctor will recommend a treatment plan based on the following factors:
- Whether your CMML is type 1 or type 2.
- Whether your CMML is more similar to an MDS or an MPN.
- Your symptoms.
- Your age.
- General health.
- Treatment preferences.
Your doctor may recommend genetic testinga procedure that analyses DNA to identify changes in genes, chromosomes and proteins, which can be used to analyse tumour DNA to help determine which treatment has the greatest chance of success, which analyses your tumour DNA and can help determine which treatment has the greatest chance of success. Your doctor will discuss the most appropriate course of treatment for you.
Treatment options for CMML may include:
- Watch and waitthe close monitoring of a cancer without giving treatment until symptoms appear or worsen.
- Supportive treatments, such as:
- Transfusion therapy.
- Antibiotics.
- Chemotherapya cancer treatment that uses drugs to kill or slow the growth of cancer cells, while minimising damage to healthy cells.
- Stem cell transplanta procedure that involves replacing unhealthy blood-forming cells (stem cells) with healthy stem cells.
- Clinical trialsresearch studies performed to test new treatments, tests or procedures and evaluate their effectiveness on various diseases.
- Palliative carea variety of practices and exercises used to provide pain relief and improve quality of life without curing the disease.
Risk factors
While the cause of CMML remains unknown, some of the following factors may increase the likelihood of developing the disease:
- Genetic mutations, potentially including:
- TET 2 gene.
- RAS gene.
- ASXL1 gene.
- SRSF2 gene.
- Previous exposure to radiation therapya treatment that uses controlled doses of radiation to damage or kill cancer cells.
- Previous exposure to chemotherapy.
Not everyone with these risk factors will develop the disease, and some people who have the disease may have none of these risk factors. See your general practitioner (GP) if you are concerned.
Symptoms
CMML may appear asymptomatic during the early stages of disease. As the cancer progresses, some of the following symptoms may appear:
- Anaemiaa condition where there aren't enough red blood cells in the blood, causing fatigue, weakness and pale skin and affecting how the body responds to infection, with symptoms potentially including:
- Fatigue.
- Dizziness.
- Weakness.
- Dyspnea.
- Paleness.
- Neutropeniaa condition where there are low levels of neutrophils (a type of white blood cell) in the body, with symptoms potentially including:
- Recurrent infections.
- Fevers.
- Mouth ulcers.
- Thrombocytopenialow levels of platelets in the blood, with symptoms potentially including:
- Easy bruising.
- Purpuraa rash of small, red dots due to small superficial capillary bleeds; generally larger than petichiae or petechiaea rash of small, red dots due to small superficial capillary bleeds; generally smaller than purpura.
- Bleeding of the nose and/or the gums.
- Unexplained weight loss/loss of appetite.
- Fever.
- Night sweats.
- Fatigue.
- Frequent and/or persistent infections.
- Easy bleeding and/or bruising.
- Splenomegalyenlargement of the spleen.
- Hepatomegalyenlargement of the liver.
- Dyspnea.
- Skin rashes and/or lumps.
Not everyone with the symptoms above will have cancer, but see your general practitioner (GP) if you are concerned.
Diagnosis
If your doctor suspects you have an CMML, they may order the following tests to confirm the diagnosis and refer you to a specialist for treatment:
- Physical examinationan examination of your current symptoms, affected area(s) and overall medical history.
- Blood teststesting done to measure the levels of certain substances in the blood.
- Bone marrow aspirationa procedure that involves inserting a needle into the hipbone (or the breastbone in some cases) to remove samples of solid and liquid bone marrow.
- Biopsyremoval of a section of tissue to analyse for cancer cells.
