What is Acute Lymphoblastic Leukaemia?
Leukaemia is a cancer of the white blood cells. White blood cells help to fight infection.
There are two different types of white blood cell – lymphoid cells (also known as lymphocytes) and myeloid cells. Normally these 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.
Acute Lymphoblastic Leukaemia is an overproduction of immature lymphoid cells, called lymphoblasts or blast cells. Immature lymphoid 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 of leukaemia in children such as bruising and anaemia are caused by the bone marrow’s inability to make enough healthy red blood cells and platelets.
Incidence
Leukaemia is the most common childhood cancer, accounting for nearly a third of all cases (31% and 29% in boys and girls, respectively) in Great Britain. ALL accounts for around four-fifths (78%) of all leukaemias diagnosed in children in the UK.
There is a peak in incidence of Acute Lymphoblastic Leukaemia in children aged two to three years; more than half of all children diagnosed with Acute Lymphoblastic Leukaemia are under the age of five years.
Boys have a greater risk than girls of developing ALL, by a factor of 4:3. The reason for this difference between the sexes is not known. Boys also require a longer duration of treatment (see below).
What are the symptoms of ALL?
Signs and symptoms of leukaemia in children and babies:
- Frequent and persistent infections
- Unusual bleeding
- Unusual bruising
- Tiredness
- Paleness
- Breathlessness and coughing
- Anemia
Childhood leukaemia develops quickly. It’s possible for some or all of these symptoms of leukaemia in children to be apparent.
A diagnosis of childhood leukaemia can be made on the basis of a blood test, which will reveal low numbers of normal white blood cells and 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.
How is ALL treated?
Whilst over 90% of Acute Lymphoblastic childhood Leukaemia cases can now be successfully treated (with survival for 5 years or more), treatment is long and gruelling, lasting two years for girls and three years for boys.
The principal treatment is chemotherapy. A combination of chemotherapy drugs and steroid medicines is given in several stages, or blocks, as outlined below.
As well as chemotherapy, some children will also require radiotherapy and/or a stem cell (bone marrow) transplant.
Remission induction
The initial aim of treatment is to achieve a state called remission where most of the leukaemic cells have been killed, allowing production of normal blood cells to resume. This stage involves the use of several drugs in combination and usually lasts between three and eight weeks, depending how quickly the child responds to treatment.
Consolidation
Almost all children will have leukaemic cells remaining when they achieve remission. This is known as minimal residual disease or MRD. It is necessary to give further blocks of treatment to eradicate the disease completely and achieve a cure. Standard consolidation therapy involves two blocks of chemotherapy at intervals of roughly four and eight months from diagnosis but protocols vary according to a number of factors including MRD status. For high-risk children, treatment may be intensified by the inclusion of additional blocks of treatment, or by the inclusion of additional drugs in the periods of maintenance therapy between the intensification blocks. Intervals of time are left between blocks of treatment in order to allow the child’s body to recover and to minimise the risk of treatment-related complications.
Central nervous system (CNS) directed therapy
Some leukaemic cells may cross the barrier into the fluid which surrounds the brain and spinal cord. The chemotherapy drugs do not penetrate this barrier very well, so it is necessary to inject the drugs directly into the fluid. This is known as an intrathecal injection. Occasionally radiotherapy may also be used to target the CNS.
Maintenance therapy
Children with ALL require a phase of extended ‘maintenance’ therapy to prevent relapse. This involves taking daily tablets and having monthly injections of chemotherapy drugs. Maintenance therapy takes the total duration of treatment to two years for girls and three years for boys. This stage of treatment is carried out on an outpatient basis, usually on a ‘shared care’ basis between the specialist centre and the child’s local hospital. Children will usually be well enough to resume most of their normal activities and return to school. They will be closely monitored during this stage.
Stem cell
Transplantation is not routinely used in the treatment of children with ALL cancer. It is only used in certain high-risk groups – in children who have relapsed early in their treatment or who have experienced more than one relapse.
Radiotherapy
Is not routinely used in the treatment of childhood acute lymphoblastic leukaemia. Children who are found to have leukaemic cells in their brain and spinal fluid when they are diagnosed may need radiotherapy. In some situations, it may be necessary for boys to have radiotherapy to their testicles since leukaemic cells can survive in the testicles despite chemotherapy.
Following completion of treatment, all children will continue to be monitored for symptoms of both disease relapse and treatment complications. Checks will take place every two or three months for the first year, gradually becoming less frequent.
Side effects
The treatments used in childhood ALL often cause side effects. Most side effects are temporary and can be minimised with good supportive care. The most common effects include:
- Nausea and vomiting
- Hair loss
- Reduced resistance to infection
- Bruising and bleeding
- Tiredness
- Diarrhoea
Follow-up and Acute Lymphoblastic Leukaemia relapse
All children will be followed-up at regular intervals after their treatment for ALL to monitor their progress and check for treatment-related problems.
Although most children with ALL will achieve remission, up to a quarter of these children will relapse – their disease will return. Most relapses occur within three years of treatment ending.
Relapsed ALL tends to be more resistant to treatment but many children can be successfully re-treated.
A stem cell transplant may be an option for some children who relapse early in treatment or who experience more than one relapse.
The likelihood of a relapse progressively decreases with time, particularly once maintenance treatment is completed.
Survival rate
The survival rate for children diagnosed with Acute Lymphoblastic Leukaemia is over 90%. ALL survival rate is highest in children diagnosed after one year of age.
Until the 1960s childhood leukaemia was incurable. Today, thanks to improvements in care and sustained investment in research, the outlook for young patients diagnosed with ALL has dramatically improved. Rian’s ALL cancer diagnosis all started with a pin prick rash.
Research
Most children have their treatment as part of a clinical trial. These aim to improve understanding of the best way to treat the childhood leukaemia, usually by comparing the standard treatment with a new or modified version. The dramatic improvement in ALL survival rate has been brought about by a continuous series of clinical trials which have pioneered new ways of treating the disease.
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