Childhood Leukaemia

by gillj099 (student)

Jane Gill Target Audience: A level Biology Students 9DPT

This text would be found in an A level textbook

Childhood Leukaemia

Leukaemia is a cancer of the blood which differs greatly from other cancers. Most cancers take the form of a solid tumour. However, in leukaemia large numbers of mutated white blood cells are produced in the bone marrow. These white blood cells crowd the bone marrow and then spill out and rapidly flood the bloodstream. However, they can’t perform their proper role as they don’t have the right properties to do so and are defective.

In the different types of leukaemia the white blood cells affected are slightly different. In the bloodstream there are two different types of white blood cells that can be affected they are known as myeloid blood cells and lymphoid blood cells.

Leukaemia often results in anaemia (low numbers of blood cells) and bleeding problems. In addition to this there is an increased risk of infection because there are defective white blood cells.

There are three main types of childhood leukaemia’s most of which are acute; this is when leukaemia progresses rapidly. The chronic form of leukaemia, which progresses slowly, is very rare in childhood.

Over 500 children are diagnosed with leukaemia in the UK every year, making it the most common form of childhood cancer. The majority of children diagnosed with cancer are under the age of 5 years.

All of the symptoms of leukaemia are quite general. All types of leukaemia have the same symptoms. These symptoms include:

Frequent persistent infections
Unusual bleeding and bruising
Tiredness
Paleness and
Breathlessness.

However, because these symptoms are not specific and leukaemia is quite rare, doctors often don’t realise that the child is suffering from leukaemia at first. If leukaemia is suspected, a blood test is taken which will reveal low numbers of red blood cells and normal white blood cells and high numbers of defective white blood cells. At this point, a child will be referred to a hospital for further tests so that the exact diagnosis can be confirmed.

Once the type of cancer has been confirmed, treatment will start which differs greatly depending on the type of leukaemia. Until the 1960s leukaemia was incurable. However, there is now a higher chance of survival with a 60% chance of survival if a child is diagnosed with CML. Overall, two thirds of all children diagnosed with AML are cured and 90% of children suffering from ALL are cured.

Acute Myeloid Leukaemia

70 cases of AML are diagnosed every year. For every four girls diagnosed with AML, five boys are diagnosed are also diagnosed with AML. Children less than 2 years ...

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Acute Myeloid Leukaemia

70 cases of AML are diagnosed every year. For every four girls diagnosed with AML, five boys are diagnosed are also diagnosed with AML. Children less than 2 years of age have the highest risk of AML. The risk for 2 to 9 year olds is low although the risk of AML sadly increases through adolescence. Over 15% of childhood leukaemia cases in the UK every year are Acute Myeloid Leukaemia (AML).

There are different sub-categories of AML. The categories are divided according which type of cells are affected, the stage of development 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. On the other hand, cells that do not show signs of becoming a particular type of white blood cell are undifferentiated. If a doctor knows the sup-type of AML, the best treatment can often be decided upon.

The most common form of classification is known as the FAB (French- American- British) system:

M0 AML with little evidence of differentiation
M1 AML without maturation (the blood cells aren’t fully developed)
M2 AML with maturation (the blood cells are fully developed)
M3 Acute Promyelocytic Leukaemia (a form of AML, it is distinctly different from all other sub-types of AML; it means that there are underdeveloped, cancerous white blood cells)
M4 Acute Myelomonocytic Leukaemia (A form of AML which affects a different type of myeloid cell, the Monocytic cell)
M5 Acute Monocytic/Monoblastic Leukaemia (A form of AML which affects Monocytic and Monoblastic cells. These are both types of Myeloid cells)
M6 Acute Erythroleukaemia (A form of AML which affects another type of myeloid cell which is called the erythroblast cell )
M7 Acute Megakaryoblastic Leukaemia (A form of AML which mainly affects the Megakaryoblastic immature dividing cells [immature dividing cells are also known as blast cells] which are another type of myeloid cell)

Treatment for AML

Children are admitted to hospital for around 6 months which is the amount of time it takes to treat AML. The intensive treatment often makes children unwell and they often need a high level of supportive care. The main treatment is chemotherapy, a combination of chemotherapy drugs and steroids are given as part of a treatment plan. Some children also require radiotherapy or a bone marrow transplant, for which they need to find a donor with the same blood group.

There are 2 phases for the treatment- remission induction (when the child is kept in special conditions and undergoes therapy) and post-remission treatment (when the child is kept in hospital and checks are made to see that the child is fully recovered)

Chronic Myeloid Leukaemia

Less than 15 new cases of CML are diagnosed in the UK every year and most of these cases are in children in the late teens. CML is exceptionally rare at any age and is most commonly found in adults with less than 5% of the total of all leukaemias are Chronic Myeloid Leukaemia (CML)

When a child suffers from CML, their myeloid cells are affected. The bone marrow is filled up with immature blood cells which stop healthy blood cells being produced.

CML is the same as AML except that the process happens slowly in that myeloid cells are affected but there is one major difference. When AML progresses relatively quickly, CML progresses slowly, often over several years.

There are three stages in the development of CML:

Chronic Phase. Often in this phase, there are no symptoms of leukaemia but immature dividing cells (blast cells) are present in the blood and bone marrow. This phase can last several years before progressing onto the second stage.
Accelerated phase. The number of blast cells in the blood and bone marrow can be found and there is evidence of the number of normal cells decreasing. This phase lasts 3 to 9 months.
Blast phase/ Blast crisis. During this third and final phase, the leukaemia greatly resembles AML with over 30% of bone marrow and blood cells being blast cells. The disease is normally fatal with 3 to 6 months of entering this phase, if there is no treatment.

Treatment for CML

The best chance for CML to be cured is with high-dose chemotherapy with a bone marrow transplant. Drugs (such as Gleevec, Sprycal and Tasigna) attack cells with the Philadelphia chromosome, which is the key genetic abnormality in CML. These drugs are normally effective at keeping CML under control for long periods of time and without any side effects. However, these drugs do not cure CML when used and so they must be taken continuously.

Acute Lymphoblastic Leukaemia

Around 370 cases of ALL are diagnosed every year in the UK with more boys being diagnosed every year. For every 3 girls diagnosed with ALL, 4 boys are also diagnosed as well. ALL is most common amongst 3 and 4 year olds with the risk of having ALL increasing rapidly after birth and then decreasing after the 4th year. More than 80% of all childhood leukaemias are Acute Lymphoblastic Leukaemia (ALL). This is the only form of cancer which is more common in children than adults. ALL affects the lymphoid cells.

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

The affected lymphoid cells can either be precursor (>98% developed) or mature.
Precursor cell leukaemias may involve either of the 2 types of lymphoid cells: B-cells (87% developed) or T-cells (13% developed).
Precursor B-cell ALL is further sub-divided into 3 categories: null-cell, common ALL and pre-B ALL

Null-Cell: this is when a lymphoid cell isn’t a T-cell or a B-cell. It is either more developed than both, or less so.
Pre-B ALL: This is when a lymphoid cell isn’t quite a B-cell. It is a bit less developed but will develop into a B-cell.
Common ALL: This is when a lymphoid cell is mature.

Common ALL accounts for 70% of childhood ALL.

Treatment

When the diagnosis of ALL is confirmed, the child will be referred immediately to one of the UK’s 21 specialist centres for treatment. The aim of the treatment is to rid the body of leukaemic cells and to restore normal blood cell production. The principal treatment is chemotherapy. Some children may require radiotherapy or bone marrow transplants.

The duration of the treatment for ALL is 2 years for girls and boys require 1 additional year as they have been shown to have a greater risk of a relapse. The child would spend the first part of their treatment in hospital but most of their later treatment will often be carried out on a ‘shared care’ basis between the specialist centre and the local hospital.

Glossary

Chemotherapy: the treatment of disease by the use of chemical substances.

Gleevec: a drug used for the treatment of CML.

Maturation: the process in which a cell becomes fully developed.

Myeloid Cells: white blood cells that are not Lymphoid Cells.

Lymphoid Cells: cells that produce immunity.

Philadelphia Chromosome: a chromosome abnormality in CML.

Precursor: something that suggests something to come.

Radiotherapy: the treatment of disease by exposure to a radioactive substance.

Sprycel: a drug used to treat AML and CML.

Steroids: Any of a large class of organic compounds with a characteristic molecular structure containing four rings of carbon atoms.

Tasigna: a drug used to treat CML when there is a Philadelphia Chromosome.