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Chronic myeloid leukaemia (CML)

Chronic myeloid leukaemia (CML) affects a type of white blood cell called a myeloid cell. These cells are a middle step between stem cells and fully-formed white blood cells.

People with CML produce too many granulocytes, a specific type of myeloid cell, that are not fully formed. This is why you may hear CML referred to as ‘chronic granulocytic leukaemia’ (CGL). Over time, these abnormal cells fill the bone marrow, which reduces the number of normal cells in the blood.

CML is not classified into different stages, but it does have three recognised phases: ‘chronic’, ‘accelerated’ and ‘blast crisis’. Very few patients progress beyond the chronic phase today due to the effectiveness of modern treatment.

CML is defined by the presence of a ‘Philadelphia Chromosome’ which forms when parts of your DNA are exchanged between two chromosomes. This causes two different genes (called ‘ABL’ and ‘BCR’) that are normally completely separate, to fuse together and promote uncontrolled cell growth.

More information on CML is available on the Blood Cancer UK and Leukaemia Care websites.

CML facts

Chronic Myeloid Leukaemia (CML)

Cell type: 
Myeloid cells, in particular granulocytes

788 / year in the UK

UK transplants:
61 in 2019

More common in people over 65

Tyrosine Kinase Inhibitors (TKI) and possibly a stem cell transplant

Other information:
TKIs allow most CML patients to live long and healthy lives


CML and stem cell transplants

Most patients with CML are diagnosed during the chronic phase, when treatment with a type of drug called Tyrosine Kinase Inhibitors (TKIs) is possible. Some TKIs are designed to stop cancer cells growing by targeting the Philadelphia Chromosome.

Stem cell transplants are only recommended:

  • if you have CML that hasn’t responded to TKIs, or
  • if you are diagnosed with ‘blast crisis’ CML and treatment gets you back to ‘chronic’ phase CML.

If you do need a transplant, it will be an allograft transplant – when stem cells are donated to you by someone else.

Living with CML

I certainly try and enjoy life more now, which sounds so cliché but it is true. Even simple things. I remember a day in particular on my own walking the dog, just a normal field, nothing special about it and just thinking: 'Wow I’m lucky, this is so nice.'

Alex, who received a stem cell transplant to treat his CML in 2016. Read his story here.

Many more patient stories are available in our Blogs section

Information published: 11/02/21
Next review due: 11/02/24

Related links

Preparing for a stem cell transplant

Having a stem cell transplant

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