Acute lymphoblastic leukaemia

The most common type of leukaemia to affect children is acute lymphoblastic (lymphoid) leukaemia (ALL).

This accounts for more than 80 per cent of all cases of childhood leukaemia.

ALL is the only form of leukaemia – and one of the few forms of cancer – that is more common in children than in adults.

About acute lymphoblastic leukaemia (ALL)

Leukaemia is a cancer of the white blood cells. White blood cells help to fight infection.

There are two different types of blood cells:

lymphoid cells (lymphocytes) and
myeloid cells.

ALL affects the lymphoid cells. Normally the white blood cells, which are produced in the bone marrow, 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.

These immature dividing cells fill up the bone marrow and stop it making healthy blood cells. As the leukaemic cells are immature, they cannot work properly. This puts the child at increased risk of infection. The overproduction of white blood cells also interferes with the production of healthy red blood cells and platelets, leading to symptoms such as anaemia and bruising.

There are a number of different types of childhood ALL. These are identified according to the type of lymphoid cells affected and at what stage during its development it becomes leukaemic.

The affected lymphocytes may be either precursor (>98 per cent) or mature
Precursor cell leukaemias may involve either of the two types of lymphocyte: B-cells (87 per cent) or T-cells (13 per cent)
Precursor B-cell ALL is further divided into three categories: null-cell, common ALL and pre-B ALL
Common ALL is the most common type of childhood ALL, accounting for up to 70 per cent of cases of childhood ALL

Incidence

Around 370 new cases of childhood ALL are diagnosed every year in Great Britain.

Incidence varies with age. Risk increases rapidly after birth, peaks around the third or fourth year of life and then declines. More than half of all children diagnosed with ALL are under the age of five years.

More boys than girls develop ALL – for every 3 girls diagnosed with ALL, 4 boys are diagnosed. The reason for this difference between the sexes is not known.

Read more: Incidence

Survival

Until the 1960s, childhood leukaemia was incurable. Today, the outlook for young patients diagnosed with ALL is good - the survival rate is approaching 90 per cent.

Of the different types of ALL, children with so-called common ALL have the best prognosis. Within this group, girls fare better than boys.

Survival is highest in children diagnosed between one and four years of age.

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. However 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 principal treatment is chemotherapy. A combination of chemotherapy drugs and steroid medicines is given according to a treatment plan (also called a protocol or regimen). The treatment is given in several stages, or blocks.

As well as chemotherapy, some children will also require radiotherapy and/or a stem cell (bone marrow) transplant.

The duration of treatment for ALL is two years for girls. Boys require an additional year of treatment as they have been shown to be at greater risk of relapse.

The child will spend some time in hospital at the beginning of treatment but much of their later treatment will be carried out on an outpatient basis – often on a ‘shared care’ basis between the specialist centre, which may be some distance from home, and the child’s local hospital.

Read more: Treating acute lymphoblastic leukaemia