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About Leukaemia


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WHAT IS LEUKAEMIA?

Most people think that leukaemia is a form of cancer of the blood. This is not strictly correct, leukaemia is really a cancer of the bone marrow.
The bone marrow is found in the marrow cavities of the long bones, ribcage and pelvis and contains many different types of cells which actually produce all the various types of blood cells.

The bone marrow is the blood-making factory of the body producing hundreds of millions of red and white blood cells each and every day of our lives.
If one of these bone marrow cells becomes cancerous it starts to grow and divide aggressively out of all control and pushes out all the normal blood making cells from the bone marrow.
Consequently normal blood production ceases and the bone marrow and blood begin to fill up with cancerous leukaemia cells which serve no useful function.

There are many different types of bone marrow cell which give rise to the various types of blood cells and it is the particular type of bone marrow cell which becomes malignant determines the type of leukaemia that develops.

Broadly speaking there are two main categories of leukaemia;

acute which starts suddenly and progresses rapidly killing the patient in a matter of weeks if left untreated.

and chronic which starts gradually and progresses slowly sometimes taking many months or even years to kill the patient.

Acute leukaemia can be divided into two main types:

acute lymphoblastic leukaemia (ALL) which affects mainly children but only relatively few adults

and acute myeloid leukaemia (AML) which affects mainly adults but relatively few children.

Chronic leukaemia similarly exists as two main types chronic lymphocytic leukaemia (CLL) which effects mainly elderly men

and chronic myeloid leukaemia (CML) which usually affects young or middle aged men and women.

Each of these main forms of leukaemia can be further subdivided into different subgroups a description of which lies outside the scope of this section.

Identifying the type of leukaemia a patient has is important because the different types of leukaemia require different treatments and the outlook (prognosis) for the patient also differs markedly depending upon the type of leukaemia.

How does Leukaemia affect the patient?

Generally patients become weak and tired and appear pale, primarily because they are anaemic due to a deficiency of red blood cells.

They often develop fevers due to infections (because of an insufficiency of certain types of white blood cells which normally defend us against infections) and bruise or bleed easily due to a lack of special particles in the blood called platelets which normally help blood to clot.

All of these signs and symptoms are due to the failure of the bone marrow to make normal blood cells owing to the fact that the useless leukaemia cells have replaced all the normal bone marrow cells.

If the patient is not treated urgently they will die from overwhelming infections, anaemia or bleeding.

Diagnosis.

The patient usually goes to see a doctor because of one or all of the above symptoms.

If the doctor is suspicious that the patient has leukaemia he will arrange for the patient to have a simple blood test. This will reveal whether there are any leukaemia cells in the blood or alternatively will show there to be an excess or deficiency in normal blood cells.

If this is shown to be the case then the patient will be asked to have a bone marrow biopsy.
This is where a small sample of bone marrow is removed with a needle and syringe, usually from the pelvis, and is inspected under the microscope by a specialist called a haematologist.

This will reveal whether normal bone marrow cells have been replaced by leukaemia cells and is the definitive test upon which the diagnosis can be made.

The haematologist also has a series of special tests that can be used on the bone marrow cells to establish the particular type of leukaemia the patient has.

What causes Leukaemia?

At a biological level we are just beginning to understand exactly what goes wrong with the interior of the cell to transform it from a normal to malignant leukaemia cell that grows out of all control.

It has become clear that certain key changes taking place in the chromosomes of leukaemia cells are responsible for their malignant characteristics.

What we are not so clear about is what causes these changes in the chromosomes in the first place.

It is clear that certain chemicals including petroleum products and pesticides can cause cancer.

We also know that radiation can cause leukaemia in animals, as can certain viruses.

In Japan a virus has been identified as causing one certain type of human leukaemia found only in Japan.

There is also evidence that genetic factors, that is inherited characteristics predispose certain individuals to developing leukaemia and other cancers.

In reality there are probably several causes of leukaemia in man and for leukaemia to arise in any one individual it may be necessary for that individual to be simultaneously exposed to more than one causative agent.

So for instance if you are unfortunate enough to contact a certain virus at the same time as being exposed to a cancer causing chemical then the outcome is that you develop leukaemia.

This is the multihit hypothesis and would account for why it is that not all of us develop cancer or leukaemia because of the necessity of being exposed to two (or more) agents simultaneously.

Equally it may be that some leukaemias have no outside cause but may arise entirely within the individual due to genetic or other factors.

Much research work is going on in this area and slowly these things will become clear to us, but for now we cannot be absolutely certain of the true causes.

What is the treatment?

Thirty years ago the diagnosis of leukaemia was virtually a death sentence, with more than 90% of patients dying from the disease.

Advances in modern drug treatments have led to spectacular improvements in survival and cure rates.

Today almost two thirds of children are cured of the most common form of childhood leukaemia, whilst almost 30% of adults are cured.

These advances have come about as a result of the use of combinations of different anti-cancer drugs.

We have learned which combinations of drugs to use and how and when to give them, as a result of carefully controlled clinical trials which have been undertaken over the past 30 years.

This form of anti-cancer therapy using powerful cytotoxic drugs is known as chemotherapy.

New clinical trials are constantly striving to improve the results by investigating new combinations of the same and new drugs and new schedules (the time during treatment at which drugs are given).

The drugs that are used to kill leukaemia cells are very powerful and also kill and damage normal cells in the body of the patient.

It is for this reason that patients receiving chemotherapy can sometimes become ill as a direct result of the treatment.

Anti-cancer drugs cause vomiting, bone marrow suppression, hair loss and in extreme cases heart, lung and liver damage.

This is why it is very important that patients undergoing chemotherapy for leukaemia are monitored regularly and receive good supportive care.

They need to receive blood and platelet transfusions to replace a deficiency of these which arises as a consequence of both the leukaemia and chemotherapy.

Sometimes patients need to be kept in isolation to avoid infections from other people and receive antibiotics directly into the bloodstream to combat infections which arise as a direct consequence of their lack of white blood cells which normally defend healthy individuals from such infections.

The supportive treatment together with the anti-leukaemia chemotherapy are the two factors which have led to the overall improvement in successful treatment for patients with leukaemia.

Bone marrow transplantation is another relatively new treatment which offers leukaemia patients the possibility of a cure when chemotherapy has failed.

Here the patient receives very high doses of anti-leukaemia drugs together with radiotherapy in an attempt to eliminate all the leukaemia cells in the patient’s body together with any remaining bone marrow cells.

The patient is then given bone marrow cells from a donor (usually a matched family member but with increasing frequency from an matched unrelated donor) directly into the bloodstream.

The new healthy bone marrow cells find their way to the bone marrow cavity in the long bones and there they start producing normal blood cells.

This type of treatment is available only for those with a suitable donor and when it is carried out will succeed in curing approximately half the patients depending on the type of leukaemia and stage of disease at transplant.

An alternative is to remove the patient’s own bone marrow and physically remove the leukaemia cells using high technology techniques.

This bone marrow is then returned to the patient after they have received high dose chemotherapy to eradicate any remaining leukaemia cells in their body. However, to date, this approach has generally not been very successful with the majority of patients treated this way eventually relapsing.