Acute myeloid leukaemia

Acute myeloid leukaemia (AML) accounts for 15% of childhood leukaemias and 5% of all childhood cancers.

Leukaemia is a cancer of the white blood cells. All blood cells are produced in the bone marrow, the spongy substance at the core of some of the bones in the body.

Bone marrow contains:

red blood cells, which carry oxygen around the body
platelets, which help the blood to clot and control bleeding
white blood cells, which help fight infection.

There are two different types of white blood cell - lymphocytes and myeloid cells. Normally these cells repair and reproduce themselves in an orderly and controlled way. In leukaemia, however, the process gets out of control and the cells continue to divide but do not mature.

Acute myeloid leukaemia is an overproduction of immature myeloid cells, called myeloblasts or blast cells.

About acute myeloid leukaemia

Immature myeloid cells fill up the bone marrow and stop it making healthy blood cells. As these cells are immature, they cannot work properly. This puts the child at increased risk of infection. Symptoms such as bruising and anaemia are caused by the bone marrow’s inability to make enough healthy red blood cells and platelets.

There are different sub-types of AML. The sub-types of AML are classified according to exactly which type of cell is affected, the stage of development (maturation) the cells are at, and whether the cells are differentiated. Cells that have started to show some of the features of myeloid cells are said to show differentiation. Cells which do not show signs of becoming a particular type of white blood cell are undifferentiated.

Knowing the sub-type of AML is important as it helps doctors to decide on the best treatment.

The most commonly used classification system for AML is the French-American-British (FAB) system:

M0 Acute myeloid leukaemia with minimal evidence of myeloid differentiation
M1 Acute myeloblastic leukaemia without maturation
M2 Acute myeloblastic leukaemia with maturation
M3 Acute promyelocytic leukaemia (APL)
M4 Acute myelomonocytic leukaemia
M5 Acute monocytic/monoblastic leukaemia
M6 Acute erythroleukaemia
M7 Acute megakaryoblastic leukaemia

Incidence of AML

Around 70 new cases of childhood AML are diagnosed every year in Great Britain.

Incidence varies with age. The highest risk is in children aged less than two years; the risk in children aged two to nine years is lower and it then rises through the adolescent years.

More boys than girls develop AML – for every four girls diagnosed with ALL, five boys are diagnosed. The reason for this difference between the sexes is not known.

Survival

Children with AML have a less positive outlook than children with ALL, the more common form of childhood leukaemia.

Overall, around two thirds of children diagnosed with AML are cured.

Infants below the age of one year and children aged 10 to 14 years have lower survival than children diagnosed at intermediate ages.

Survival is highest for children with the M3 FAB sub-type.

Diagnosis

Childhood leukaemia develops quickly. The symptoms are quite general, including

frequent, persistent infections
unusual bleeding and bruising
tiredness
paleness and
breathlessness.

Children may have some or all of these symptoms.

Because these symptoms are not very specific, and because leukaemia is rare, the child’s doctor may not initially suspect leukaemia. Once leukaemia is suspected, a blood test will reveal low numbers of normal white blood cells and the presence of large numbers of abnormal white blood cells.

At this point, the child will be referred to hospital for further tests. A sample of bone marrow will be taken to confirm the exact diagnosis.

Treatment

When a diagnosis of leukaemia is confirmed, the child will be referred immediately to one of the UK’s 21 specialist paediatric oncology centres for treatment.

Further tests will be carried out to provide doctors with as much information as possible before commencing treatment.

The aim of treatment is to rid the body of leukaemic cells and restore normal blood cell production.

The total duration of treatment for AML is around six months. Children will usually be admitted to hospital for the full duration of their treatment. This is because the intensive treatment can make children very unwell and they need a high level of supportive care.

The main treatment is chemotherapy. A combination of chemotherapy drugs and steroid medicines is given according to a treatment plan (also called a protocol or regimen). Some children may also require radiotherapy and/or a stem cell (bone marrow) transplant.

There are two phases of treatment for childhood AML – remission induction and post-remission treatment.

Read more: Treating acute myeloid leukaemia

Related Topics acute myeloid leukaemia, leukaemia, Chronic myeloid leukaemia, leukaemia incidence, acute lymphoblastic leukaemia, leukaemia causes

Acute myeloid leukaemia

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