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Lymphocytes are white blood cells that produce antibodies; they are vital parts of the body’s immune system. There are two main types of lymphocytes: B and T cells.
In ALL there is an accumulation in the bone marrow of immature lymphocyte precursor cells, called blast cells. Eventually the production of normal blood cells is affected by this, resulting in a reduction in the numbers of red cells, normal white cells and platelets in the blood.
ALL is the only form of leukaemia that is more common in children than adults. It is the single most common form of paediatric cancer, accounting for about one-third of all cases in children. About 85% of cases of childhood leukaemia are ALL and it occurs in about 400 children in the UK each year. ALL occurs mostly between the ages of about two and four years. Males are affected more often than females at all ages.
What causes ALL?
There is no single proven cause of childhood ALL but there are a number of suggested causes, some of which are more controversial than others.
Children exposed to higher levels of ionizing radiation before they are born or in early life have been shown to have a high risk of developing childhood leukaemia. One theory is that delayed exposure to a common infection may rarely result in the development of leukaemia.
There is no evidence proving that exposure to high-voltage power lines causes leukaemia.
Many of the symptoms of ALL are due to the fact that the leukaemia cells multiply in the bone marrow and stop the production of healthy blood cells. Common symptoms include:
- fever and infection
- swollen glands
- limb pains.
Tests and investigations
Doctors will need to carry out tests to help decide the best treatment for your child. These tests include:
- blood tests to show if there are any leukaemia cells in the bloodstream and how the other blood cells are affected.
- chest X-ray to show whether any of the lymph glands in the chest are enlarged
- bone marrow aspirate to show what type of ALL your child has
- lumbar puncture to see whether there are any leukaemia cells in the spinal fluid.
The aim of treatment for acute lymphoblastic leukaemia (ALL) in children is to achieve a state called remission where almost all leukaemia cells have been killed and, by further treatment, to completely eradicate the disease and achieve a cure.
ALL needs intensive treatment with chemotherapy initially followed by a prolonged maintenance phase of less intensive chemotherapy. The exact details of treatment will depend upon factors such as age, the number of leukaemic blasts in the blood at diagnosis, the response to treatment and the genetic features of the leukaemic cells. Following the initial period, most of the treatment is administered as an outpatient. Boys usually receive approximately three years of treatment and girls two years.
These are the different phases of treatment:
This usually consists of intermittent chemotherapy given over approximately four weeks. The aim is to destroy as many leukaemia cells as possible.
Response to the induction will be checked by examining the bone marrow after one to two weeks of treatment and at the end of induction. The aim is for there to be a significant reduction in the number of leukaemic blasts after one to two weeks and no evidence of leukaemia in your child’s bone marrow after induction is completed (remission).
Further chemotherapy is given to destroy any leukaemia cells that may be left and prevent the leukaemia coming back. The number of courses may vary if your child takes part in a clinical trial. This is explained in more detail in the specific trial information sheet.
Central nervous system (CNS) directed therapy
ALL sometimes develops around the brain and spinal cord. This can be prevented by injecting anti-cancer drugs directly into the spinal fluid (intrathecal chemotherapy) during a lumbar puncture. This is administered more frequently in the induction and post-remission phases, and then usually every three months during maintenance therapy.
Continuation or maintenance therapy
This involves giving low-dose daily oral chemotherapy and monthly injections of chemotherapy. The dose of chemotherapy is adjusted according to a weekly blood count. Usually the children are reasonably well during this phase of treatment and the visits to hospital should be less frequent.
Bone marrow transplant
This is reserved for a few children who don’t do so well with standard chemotherapy or if the leukaemia comes back. The chromosome studies will help your doctors decide whether your child needs a bone marrow transplant. About 2–3% of children require a bone marrow transplant.
If your child takes part in a clinical trial for acute lymphoblastic leukaemia, the treatment is explained in more detail in the specific trial information sheet. You will be given an outline of the treatment in the form of a ‘road map’.
Many children with acute lymphoblastic leukaemia (ALL) are now cured with current treatment. However, the prognosis depends on how well your child responds to treatment and some of the features of the leukaemic cells such as the chromosomes.
General side effects of chemotherapy
Bone marrow suppression (myelosuppression)
Chemotherapy drugs decrease the production of blood cells by the bone marrow for a variable period of time. This results in low levels of red blood cells (anaemia), white blood cells (neutropenia) and platelets (thrombocytopenia). Your child may need blood or platelet transfusions and will be at increased risk of infections. The doctors and nurses caring for your child will tell you more about these side effects.
Nausea and vomiting
Some of the chemotherapy drugs used may make your child feel sick or vomit. However, anti-sickness drugs can be given at the same time to stop nausea and vomiting.
Sore mouth (mucositis)
Some of the chemotherapy drugs make the lining of the mouth and throat very sore and ulcerated. Your doctor will give your child painkillers for this, and explain how to care for your child’s mouth during treatment.
Temporary hair loss is common.
A small number of children may develop long-term side effects related to the treatment. These include impaired heart function and a small increased risk of a second cancer in later life.
A few children are treated with cranial radiotherapy – this may result in problems with growth and puberty and reduced educational achievement.
Once treatment has finished your child will continue to be seen in the outpatient department where doctors will help treat any long-term effects.