Acute myeloid leukaemia
What is it ?
Acute myeloid leukaemia (AML) is a type of cancer that affects the blood and bone marrow. AML is characterised by an overproduction of immature white blood cells, called myeloblasts or leukaemic blasts. These cells crowd the bone marrow, preventing it from making normal blood cells. They can also spill out into the blood stream and circulate around the body. Due to their immaturity they are unable to function properly to prevent or fight infection. Inadequate numbers of red cells and platelets being made by the marrow cause anaemia, and easy bleeding and/or bruising.
Acute myeloid leukaemia is sometimes called acute myelocytic, myelogenous or granulocytic leukaemia.
Which type of AML do I have ?
AML is not a single disease. It is the name given to a group of leukaemias that develop in the myeloid cell line in the bone marrow. Some years ago doctors from America, France and Britain decided to classify AML into eight different subtypes based on the appearance of the leukaemic cells under the microscope. Each subtype provides information on the type of blood cell involved and the point at which it stopped maturing properly in the bone marrow. This is known as the French-American-British (FAB) classification system.
The current World Health Organization’s classification system for AML uses additional information, obtained from more specialised laboratory techniques, like genetic studies, to classify AML more precisely. This information also provides more reliable information regarding the likely course (prognosis), of a particular subtype of AML, and the best way to treat it.
The most important factor in predicting prognosis in AML is the genetic make-up of the leukaemic cells. Certain cytogenetic changes are associated with a more favourable prognosis than others. This means that they are more likely to respond well to treatment, and may even be cured. Favourable cytogenetic changes include: a translocation between chromosome 8 and 21 t(8;21), inversion of chromosome 16; inv(16) and a translocation between chromosome 15 and 17; t(15;17). This final change is found in a subtype of AML called acute promyelocytic leukaemia (APML or M3). APML is treated differently to other types of AML, and usually has the best overall prognosis.
Other cytogenetic changes are associated with an average or intermediate prognosis, while others still are associated with a poor, or unfavourable prognosis. It is important to note that in most cases of AML, neither ‘good’ or ‘bad-risk’ cytogenetic changes are found. People with ‘normal’ cytogenetics are also regarded as having an average prognosis.
Some subtypes of AML are associated with specific symptoms. For example, in some subtypes of AML, leukaemic cells can spread from the blood stream into other parts of the body like the gums, causing swelling and discomfort in this area. Acute promyelocytic leukaemia (APML or M3) is associated with bleeding and abnormalities in blood clotting.
How common is it ?
Each year in Australia around 715 people are diagnosed with AML*. Overall AML is rare disease, accounting for 0.8 per cent of all cancers diagnosed, at a rate of 3.7 per 100,000 of the population.
Who gets it ?
AML can occur at any age but is more common in adults over the age of 60 years. Around 50 children (0-14 years) are diagnosed with AML in Australia each year. It occurs more frequently in males than in females.
What causes AML?
In most cases the causes of AML remain largely unknown but it is thought to result from damage to one or more of the genes that normally control blood cell development . Research is going on all the time into possible causes of this damage and certain factors have been identified that may put some people at an increased risk. These include exposure to:
- very high doses of radiation, either accidentally (nuclear accident) or therapeutically (to treat other cancers)
- industrial chemicals like benzene over a long period, certain types of chemotherapy to treat other cancers and
- cancer-causing substances in tobacco smoke
Some people with pre-existing blood disorders like certain myelodysplastic syndromes (MDS) and myeloproliferative disorders (MPD), or certain genetic disorders like Down's syndrome, Bloom syndrome and Fanconi's anaemia may have a higher than average risk of developing AML.
What are the symptoms?
The main symptoms of AML are caused by a lack of normal blood cells. These include:
- anaemia due to a lack of red cells ; causing persistent tiredness, dizziness, paleness, or shortness of breath when physically active
- frequent or repeated infections and slow healing, due to a lack of normal white cells, especially neutrophils
- increased or unexplained bleeding or bruising, due to a very low platelet count.
Other symptoms may include bone pain, swollen lymph nodes, swollen gums, chest pain and abdominal discomfort due to a swollen spleen or liver.
How is it diagnosed?
AML is diagnosed by a full blood count (FBC) and a bone marrow bipsoy/examination.
How is it treated?
Because it progresses quickly, treatment needs to begin soon after AML is diagnosed. The type of treatment used will depend on a number of factors including the sub-type of AML, the genetic make-up of the leukaemic cells, your age and general health.
Chemotherapy is the main form of treatment for AML. Initially the aim of treatment is to destroy leukaemic cells and induce a remission. This means that there is no evidence of leukaemic cells in the blood and bone marrow and that normal blood cell production and normal blood counts are restored. Once a remission has been achieved, more chemotherapy is given to try to prevent the leukaemia from returning (relapsing). This is called post-remission or consolidation therapy.
Chemotherapy is usually given as a combination of drugs, usually over a period of a week or so. In most cases the drugs are given as infusions through a special line called a central venous catheter, which will be inserted before you start treatment.
People with a sub-type of AML called acute promyelocytic leukaemia (APML) may also be treated with a non-chemotherapy drug called all-trans retinoic acid (ATRA), a derivative of vitamin A which helps make the leukaemic cells either mature properly, or die.
Occasionally, a stem cell transplant may be used which increases the chance of cure for some people with AML.
What are the side effects of treatment?
All treatments can cause side effects. The type and severity however will vary between individuals, depending on the type of treatment used and how an individual responds to it. In general, more intensive treatment is associated with more severe side-effects. It is important to report any symptoms you are having to your doctor or nurse. In most cases they can be treated and are reversible.
Although AML affects the bone marrow's ability to produce adequate numbers of blood cells and platelets, chemotherapy affects this ability further. Blood counts generally fall within a week of treatment and may take some time to recover, depending on the type and doses of drugs used. During this time you are likely to need antibiotics and other drugs to treat, or prevent infection. You are also likely to need blood transfusions to treat severe anaemia, and platelet transfusions to reduce the risk of bleeding.
Other possible side effects of chemotherapy include:
- feeling sick - nausea and/or vomiting
- feeling tired and weak
- hair loss and thinning
- mouth problems such as mucositis or ulcers
- diarrhoea or constipation
- skin problems sych as dryness, ras or sensitivity to sunlight
- fertility problems
Your doctor and nurse will discuss with you the possible side-effects of your treatment and how they can be managed.
For further information click on the links below:
- Stem cell transplants
- Myelodysplastic syndromes
- Chronic myeloproliferative disorders
- Living with blood cancer