Chronic myeloid leukaemia (CML) is a cancer of the blood. There are three phases of CML and most patients are diagnosed in the early or chronic phase. In this phase your body makes too many mature white blood cells called granulocytes.

95% of cases of CML are caused by development of a chromosome abnormality of chromosome 9 and 22. This is when, as the cell divides a small part of chromosome 9 becomes attached to a small part of chromosome 22. This process is called a translocation. The new, shorter chromosome 22 formed by the translocation has been named the Philadelphia chromosome. The translocation also forms a new fusion gene called BCR-ABL1, which in turn makes a new protein (an enzyme known as tyrosine kinase), which causes leukaemia stem cells to divide more often and become greater in number.

In its early stages, CML usually causes no noticeable symptoms. As the condition develops, the abnormal granulocytes can collect in the spleen, making it swell. They can also overcrowd the bone marrow, meaning there isn’t room for other blood cells to be made. Symptoms may include:

  • tiredness, often caused by anaemia
  • loss of appetite
  • unexplained weight loss
  • increased sweating, particularly at night
  • a feeling of abdominal bloating, swelling and occasionally pain
  • blurred vision
  • unusual or excessive bleeding or bruising
  • swollen lymph nodes
  • bone pain

CML is quite a rare type of cancer. There are around 750 new cases of CML in the UK every year. CML can affect people of any age, although is rare in children under the age of 15. The average age at diagnosis is about 60 and slightly more men than women get it. There is no evidence that it runs in families and the only known risk factor for developing CML is being exposed to very high levels of ionising radiation. It is extremely unlikely anyone living in the UK would be exposed to a level of radiation high enough to increase their risk of developing CML.

About nine in 10 patients with CML will be diagnosed within the stable (chronic) phase of the disease. With the advent of medication to inhibit the growth of CML, most of these patients will be able to stay within the chronic phase for life. It is rare nowadays for people diagnosed within the chronic phase to progress to a more advanced phase, but it can happen. If you enter these advanced phases, your doctor and clinical nurse specialist will discuss w your individual outlook and treatment plan.