What is chronic myeloid leukaemia?
Leukaemia is cancer of the white blood cells. Chronic leukaemia means the condition progresses slowly over the course of many years.
Chronic leukaemia is classified according to the type of white blood cells that are affected by cancer. There are two main types:
- lymphocytes - mostly used to fight viral infections
- myeloid cells - which perform a number of different functions, such as fighting bacterial infections, defending the body against parasites and preventing the spread of tissue damage
These pages focus on chronic myeloid leukaemia, which is cancer of the myeloid cells. The following other types of leukaemia are covered elsewhere:
Warning signs of chronic myeloid leukaemia
In its early stages, chronic myeloid leukaemia usually causes no noticeable symptoms. As the condition develops, symptoms include:
- weight loss
- night sweats
- a feeling of bloating
- bone pain
Read more about the symptoms of chronic myeloid leukaemia.
What happens in chronic leukaemia
All of the blood cells in your body are produced by bone marrow. Bone marrow is a spongy material found inside the bones. It is important because it produces special cells called stem cells.
Stem cells are very useful because they have the ability to create other specialised cells that carry out important functions. The stem cells in bone marrow produce three important types of blood cells:
- red blood cells - which carry oxygen around the body
- white blood cells - which help fight infection
- platelets - which help stop bleeding
In leukaemia, the cancer begins in the stem cells and causes them to produce more white blood cells than are needed. Over time, the cancerous white blood cells build up, disrupting the normal balance of cells in the blood.
This means that the body does not have enough red blood cells or platelets. This can cause symptoms of anaemia, such as tiredness, as well as increasing the likelihood of excessive bleeding.
How common is chronic myeloid leukaemia?
Chronic leukaemia is an uncommon type of cancer.
Chronic myeloid leukaemia can affect people of any age, but it is more common in people aged 40-60. There is no evidence that it runs in families.
The outlook for chronic myeloid leukaemia depends to a large extent on how well a person responds to medication.
Most patients (60-65%) do really well on imatinib tablets, which are taken every day for life.
For those who don't do well on imatinib, about half respond to one of the alternative drugs (nilotinib or dasatinib or bosutinib).
Those who fail these drugs or cannot tolerate them will be offered ponatinib or a bone marrow transplant.
Read more about the Treatment of chronic myeloid leukaemia.
Chronic myeloid leukaemia symptoms
In its early stages, chronic myeloid leukaemia usually causes no noticeable symptoms.
When symptoms do develop, they typically include:
- loss of appetite
- weight loss
- a feeling of bloating
Chronic myeloid leukaemia can also cause swelling in your spleen (an organ that helps to filter impurities from your blood). This can cause a lump to appear on the left side of your abdomen, which may be painful when touched. A swollen spleen can also put pressure on your stomach, causing a lack of appetite and indigestion.
The symptoms of chronic myeloid leukaemia in its advanced stage will be much more noticeable and troublesome. They include:
- severe fatigue
- bone pain
- night sweats
- easily bruised skin
Chronic myeloid leukaemia causes
Chronic myeloid leukaemia begins with an alteration to the structure of the DNA found in the stem cells responsible for producing white blood cells. This is known as a genetic mutation.
The DNA provides the cells with a basic set of instructions, such as when to grow and reproduce. The mutation in the DNA changes these instructions so that stem cells produce more white blood cells than are needed.
The white blood cells are also produced when they are still immature, so they do not have the infection-fighting properties of healthy 'adult' white blood cells.
Eventually, as the number of immature cells (blast cells) increases, it leads to a corresponding decrease in red blood cells and platelets. This reduction in other types of healthy blood cells causes many of the symptoms of chronic leukaemia.
Possible triggers for chronic leukaemia
What triggers the development of chronic leukaemia and causes the initial mutation in stem cells is unknown. The one proven risk factor is exposure to radiation.
However, radiation is only a significant risk if the levels are extremely high, such as those recorded after an atomic bomb explodes, or those released after a nuclear reactor accident, such as the one at Chernobyl.
There is limited evidence that prolonged exposure to the chemical benzene leads to an increased risk of chronic myeloid leukaemia. Benzene is found in petrol and is also used in the rubber industry, but there are strict controls to protect people from prolonged exposure.
Benzene is also found in cigarettes. However, it is thought that smoking is more of a risk factor in acute leukaemia than it is in chronic leukaemia.
A number of occupations have been linked to an increase risk of chronic leukaemia, possibly due to exposure to certain substances such as pesticides or chemicals.
These occupations include:
- all types of agricultural workers
- people who are involved with rubber or plastic manufacture
- tailors and dressmakers
- builder’s labourer
Diagnosing chronic myeloid leukaemia
Suspected cases of chronic myeloid leukaemia are usually first detected after a blood test, which has often been carried out to diagnose another unrelated condition.
A blood test that reveals abnormally high levels of white blood cells could be a sign of chronic leukaemia. If you have a blood test with abnormal results, you will be referred to a haematologist (a specialist in treating blood conditions) for further testing.
Bone marrow biopsy
To confirm a diagnosis of chronic leukaemia, the haematologist will take a small sample of your bone marrow to examine under a microscope. This procedure is known as a bone marrow biopsy. A bone marrow biopsy is usually carried out under a local anaesthetic.
The haematologist will numb an area of skin at the back of your hip bone, before using a needle to remove the bone marrow sample. The procedure is usually painless although you may experience some bruising and discomfort for a few days afterwards. The procedure takes around 15 minutes to complete and you should not have to stay in hospital overnight.
The bone marrow sample will be checked to see if there are cancerous cells. If there are, the biopsy will also be able to help determine which type of chronic leukaemia is present.
There are a number of additional tests that can be used to help reveal more information about the progress and extent of the leukaemia. These can also provide an insight into how the leukaemia should be treated. These are outlined below.
Cytogenetic testing involves identifying the genetic make-up of the cancerous cells. There are a number of specific genetic variations that can occur during leukaemia and knowing what these variations are can have an important impact on treatment.
For example, 90% of people with chronic myeloid leukaemia have the Philadelphia chromosome. People who have this chromosome are known to respond well to a medicine called imatinib.
Chronic myeloid leukaemia treatment
Imatinib tablets are usually given as soon as you have been diagnosed with chronic myeloid leukaemia, to slow its progression. These tablets are taken every day for life, and most patients do really well on them.
The aim of treatment is to achieve the following:
- by 3 months, correct the blood count
- by 12 months, clear the bone marrow of cells containing the Philadelphia chromosome (see Causes page for information on this)
- by 18 months, get to a stage where the leukaemia can only be detected by a very sensitive molecular test (molecular remission)
Chemotherapy is usually offered if the cancer reaches an advanced stage.
These treatments are explained below.
Treating early-stage chronic myeloid leukaemia
A medicine called imatinib is the main treatment recommended for chronic myeloid leukaemia. It is usually given as soon as a diagnosis is made because the medicine is designed to slow the progression of the cancer and to prevent the condition reaching the accelerated or advanced phase.
Imatinib is a type of tyrosine kinase inhibitor. This means it blocks a protein called tyrosine kinase (tyrosine kinase helps to stimulate the growth of cancer cells). This reduces the production of abnormal white blood cells.
Imatinib is taken as a tablet. The side effects of imatinib are usually mild and should improve with time. They include:
- swelling in the face and lower legs
- muscle cramps
It is estimated that 10-40% of people who take imatinib become resistant to its effects, so an alternative treatment is required.
Nilotinib works in a similar way to imatinib in that it blocks the effects of proteins that help stimulate the growth of cancer cells.
Side effects of nilotinib include:
- abdominal pain
- bone and joint pain
- dry skin
- loss of appetite
- hair loss
- night sweats
- tingling or numbness
If the side effects become particularly troublesome, temporarily stopping the treatment usually helps to bring them under control. Treatment can then be resumed, possibly using a lower dose of medication.
Read about the complications of chronic myeloid leukaemia for more information and advice about being vulnerable to infection and bleeding.
Treating advanced chronic myeloid leukaemia
Once chronic myeloid leukaemia has progressed to a more advanced stage, chemotherapy is the next treatment.
Chemotherapy tablets are usually used first because they have fewer and milder side effects than chemotherapy injections. Side effects include:
- skin rash
- increased vulnerability to infection
Chemotherapy can weaken your immune system, which helps protect you against infection. This is known as being immunocompromised. See chronic leukaemia – complications for more information about this.
If your symptoms persist or get worse, chemotherapy injections (intravenous chemotherapy) will need to be used. Intravenous chemotherapy causes more side effects than chemotherapy tablets and they tend to be more severe.
Side effects include:
- hair loss
These side effects should resolve after your treatment has finished, although there is a risk that infertility could be permanent.
Bone marrow and stem cell transplants
A bone marrow transplant can offer a cure for chronic leukaemia, although it is only suitable and necessary for some patients.
Before transplantation can take place, the person receiving the transplant has to have aggressive, high-dose chemotherapy and radiotherapy to destroy any cancerous cells in their body.
This can put enormous strain on the body and can cause significant side effects and potential complications. Transplantations have better outcomes if the donor has the same tissue type as the person who is receiving the donation. The best candidate to provide a donation is usually a brother or sister with the same tissue type.
Due to these issues, transplantations are usually only successful when they are carried out in children and young people, or older people in good health, and there is a suitable brother or sister who can provide a donation.
In most cases of chronic leukaemia, the potential risks of transplantation far outweigh any benefit. For example, the chances of an elderly person with advanced chronic leukaemia surviving a bone marrow transplant can be as low as one in five.
However, your specific circumstances may mean that the benefits of treatment outweigh the risks.
Read more about bone marrow transplants.
Complications of chronic myeloid leukaemia
Being compromised (having a weakened immune system) is a possible complication for some patients with chronic leukaemia.
There are two reasons for this:
- the lack of healthy white blood cells means that your immune system is less able to fight infection
- many of the medicines used to treat chronic leukaemia can weaken the immune system
This means that you are more vulnerable to developing an infection, and that any infection you have has an increased potential to cause serious complications.
You may be advised to take regular doses of antibiotics to prevent infections occurring. You should immediately report any possible symptoms of an infection to your doctor or care team because prompt treatment may be required to prevent serious complications.
Symptoms of infection include:
- high temperature (fever) of 38C (101.4F) or above
- aching muscles
Avoid contact with anyone who is known to have an infection, even if it is a type of infection that you were previously immune to, such as chickenpox or measles. This is because your previous immunity to these conditions will probably be suppressed (lowered).
While it is important to go outside on a regular basis, both for exercise and for your psychological wellbeing, avoid visiting crowded places and using public transport during rush hour.
Also ensure that all of your vaccinations are up-to-date. Your doctor or care team will be able to advise you about this. You will be unable to have any vaccine that contains activated particles of viruses of bacteria such as:
- the mumps, measles and rubella (MMR) vaccine
- the polio vaccine
- the oral typhoid vaccine
- the BCG vaccine (used to vaccinate against tuberculosis)
- the yellow fever vaccine
Psychological effects of chronic leukaemia
Receiving a diagnosis of chronic leukaemia can be very distressing, particularly if it is unlikely that your condition can be cured. At first, the news may be difficult to take in.
The situation can be made worse if you are confronted with the knowledge that even though your leukaemia may not currently be causing any symptoms, it could be a serious problem in later life. Having to wait many years to see how the leukaemia develops can be immensely stressful and can trigger feelings of anxiety and depression.
If you have been diagnosed with leukaemia, talking to a counsellor or psychiatrist (a doctor who specialises in treating mental health conditions) may help you to combat feelings of depression and anxiety. Antidepressants or medicines that help to reduce feelings of anxiety may also help you cope better with the condition.
You may find it useful to talk to other people who are living with leukaemia. Your doctor or multidisciplinary team may be able to provide you with details of local support groups.