Tests and treatment for chronic myelomonocytic leukaemia (CMML)

Chronic myelomonocytic leukaemia (CMML) is a rare type of blood cancer. In CMML there are too many monocytes in the blood. Monocytes are a type of white blood cell.

Tests for chronic myelomonocytic leukaemia (CMML)

Many people are diagnosed with CMML because doctors find abnormal monocytes during a blood test for something else. Your doctor may then arrange a number of tests for you, including:

  • blood tests to look at how many blood cells you have and whether they are normal
  • a bone marrow test

Your doctor may also do tests on the bone marrow to look for changes in the chromosomes Open a glossary item of the CMML cells. Chromosomes contain the genetic material inside cells. These tests are called cytogenetics (pronounced sigh-toe gen-et-ics).

Doctors are learning more about CMML all the time. You might have other tests done on the bone marrow to look for other gene changes. You might hear this called myeloid next generation sequencing (NGS).

Treatment for CMML

For most people CMML is treatable, but for most people it is not curable. They can have a good quality of life while having treatment for CMML.

The type of treatment you need depends on:

  • the type of CMML you have
  • whether you have symptoms
  • your age and whether you have any other medical conditions

You and your specialist discuss your treatment plan before you start.

Watchful waiting

If you have no or few symptoms you might not need treatment at first. Instead, you will have regular check ups including blood tests. You might hear this called watchful waiting or active monitoring. You also get advice on keeping well, for example information on exercise and healthy eating.  

If your symptoms get worse or the disease progresses, you usually start treatment for CMML.

Supportive treatment

Most people need supportive treatment at some point. The treatment you need depends on the type of symptoms you have. You might need a combination of treatments.

Blood and platelet transfusions

You might have blood transfusions if your red blood cells Open a glossary item are low. If your platelets Open a glossary item are low you might require platelet transfusions, especially if you are experiencing any symptoms of bleeding.

Having a lot of blood transfusions can cause a build up of iron in your body. Red blood cells contain iron and your body stores this. But too much iron in your body can damage your heart and liver. To stop this, you might need to take medicines to get rid of the extra iron. 


You might also need to take antibiotics to treat infection. And sometimes to prevent infection.

Growth factors

Growth factors are drugs that encourage your bone marrow to make more blood cells.

Erythropoietin is a growth factor that increases the number of red blood cells. You might have this if your red blood cell level is low.

Your nurse or doctor will give you more information about these supportive treatments. 

Chemotherapy for CMML

Chemotherapy is a type of anti cancer drug treatment. The drugs work by disrupting the growth of cells and stopping them from dividing.

You can have chemotherapy as a tablet, an injection just under your skin, or as an injection into a vein. You might have just one drug or a combination of drugs.

The type of chemotherapy you have depends on your type of CMML and your general health. Chemotherapy treatments that are commonly used include: 

  • azacytidine
  • hydroxycarbamide 


Azacitidine is a type of drug called a hypomethylating agent. It works by switching off a protein called DNA methyltransferase. This switches on genes that stop the cancer cells growing and dividing. This reduces the number of abnormal blood cells and helps to control cell growth.

You usually have azacitidine as an injection just under your skin (subcutaneously) given by your nurse. You usually have this at the hospital. 

Hydroxycarbamide (hydroxyurea)

You might have hydroxycarbamide to help control a high white cell count. Hydroxycarbamide is one of a group of chemotherapy drugs known as anti metabolites. These drugs stop cells making and repairing DNA. Cancer cells need to make and repair DNA in order to grow and multiply.

You usually take this as an oral capsule every day.

Low dose cytarabine

You might have low dose cytarabine if you are not able to have hydroxycarbamide. But this treatment is not commonly used.

Your nurse or doctor will give you more information about your chemotherapy and any possible side effects.

Donor stem cell transplant

A donor stem cell transplant might be a treatment option for a few people with CMML. A donor stem cell transplant means you have a transplant using another person’s stem cells. It is called an allogeneic transplant.  

This type of transplant is usually only suitable for people who:

  • are younger

  • are in reasonably good health, apart from your CMML

  • have a suitable donor (sibling or unrelated)

 This is an intensive treatment and it has many risks. This is why it’s not suitable for everyone.


Researchers around the world are looking at better ways to treat myeloproliferative or myelodysplastic disorders. And manage treatment side effects. These clinical trials sometimes include people who have CMML.

A study is setting up a record or ‘registry’ of information about a large number of people across Europe with blood cancers including CMML. If you take part, the team will collect information about your medical history, test results and treatments. Doctors also want to find out as much as possible about the many different types of myelodysplastic or myeloproliferative disorders and how best to treat them.

Cancer Research UK Clinical Trials Database

Go to Cancer Research UK’s clinical trials database if you are looking for a trial for CMML in the UK. There might not be any open trials at the moment. But you can read about the closed trials and look at trial results.

It takes time before the results are available. This is because the trial team follow the patients for a period of time and collect and analyse the results.

Talk to your specialist if there are any trials that you think you might be able to take part in. 

Coping with CMML

Coping with a rare condition can be difficult, both practically and emotionally. Being well informed about your condition and its treatment can help you to make decisions and cope with what happens.

  • Diagnosis and Treatment of Chronic Myelomonocytic Leukemias in Adults

    Jihyun Kwon

    Blood Research, 2021. Volume 56, Supplement 1, Pages 5–16.

  • Cancer Research UK Clinical Trials Database

    Accessed December 2023

  • Myelodysplastic Syndrome/Myeloproliferative Neoplasm (MDS/MPN) Overlap Syndromes: Molecular Pathogenetic Mechanisms and Their Implications

    H Pati and K Kundil Veetil

    Indian Journal of Haematology and Blood Transfusions 2019. Volume 35, Issue 1, Pages 3–11.

  • The 5th edition of the World Health Organization Classification of Haematolymphoid Tumours: Myeloid and Histiocytic/Dendritic Neoplasms

    J D. Khoury and others

    Leukemia, 2022. Volume 36, pages 1703–1719

Last reviewed: 
23 Jan 2024
Next review due: 
23 Jan 2027

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