Leucemia

O que é leucemia?

Leukaemia is a cancer of cells in the bone marrow (the cells which develop into white blood cells).

Cancer is a disease of the cells in the body. There are many tipos de câncer which arise from different types of cell. What all cancers have in common is that the cancer cells are abnormal and do not respond to normal control mechanisms. Large numbers of cancer cells build up because they multiply 'out of control', or because they live much longer than normal cells, or both.

With leukaemia, the cancerous cells in the bone marrow spill out into the bloodstream. There are several types of leukaemia. Most types arise from cells which normally develop into white blood cells. (The word leukaemia comes from a Greek word which means 'white blood'.)

If you develop leukaemia it is important to know exactly what type it is. This is because the outlook (prognosis) and treatments vary for the different types. Before discussing the different types of leukaemia it may help to know some basics about normal blood cells and how they are made.

• Acute lymphoblastic leukaemia (ALL).

• Chronic lymphocytic leukaemia (CLL).

• Acute myeloid leukaemia (AML).

• Chronic myeloid leukaemia (CML).

There are various 'subtypes' of each of these. In addition there are some other rare types of leukaemia. The word:

• 'Agudo' significa que a doença se desenvolve e progride bastante rapidamente.

• 'Chronic' means persistent or ongoing. When talking about leukaemia, the word chronic also means that the disease develops and progresses slowly (even without treatment).

• 'Lymphoblastic' and 'lymphocytic' mean that an abnormal cancerous cell is a cell that originated from a lymphoid stem cell.

• 'Mieloide' significa que uma célula cancerosa anormal é uma célula que se originou de uma célula-tronco mieloide.

A leukaemia is thought to start first from one abnormal cell. What seems to happen is that certain vital genes which control how cells divide, multiply and die, are damaged or altered. This makes the cell abnormal. If the abnormal cell survives it may multiply 'out of control' or survive a long time, and develop into a leukaemia.

In most cases of leukaemia, the reason why a cell becomes abnormal is not known. There are certain 'risk factors' which increase the chance that certain leukaemias will develop, but these only account for a small number of cases.

Risk factors for some types of leukaemia

• Radiation exposure is known to be a risk factor. For example, previous radiotherapy for another condition. Additionally many of the survivors of the atom bomb used in World War II developed leukaemia due to the fall-out of radiation.

• Tratamento anterior com quimioterapia ou outros medicamentos que enfraquecem o sistema imunológico.

• Certain genetic disorders, of which the most common is síndrome de Down.

• Exposure to certain chemicals, such as benzene.

À medida que grandes quantidades de células sanguíneas anormais são produzidas, grande parte da medula óssea se enche com essas células anormais. Por causa disso, é difícil para as células normais na medula óssea sobreviverem e produzirem células sanguíneas maduras normais suficientes. Além disso, as células anormais se espalham para a corrente sanguínea. Portanto, os principais problemas que podem se desenvolver incluem:

Anemia

This occurs as the number of red blood cells in the bloodstream goes down. This can cause tiredness, breathlessness and other symptoms. You may also look pale.

Problemas de coagulação sanguínea

This is due to low levels of platelets in the bloodstream. This can cause easy bruising, bleeding from the gums and other bleeding-related problems.

Infecções graves

The abnormal white blood cells do not protect against infection. Also, there is a reduced number of normal white blood cells which usually combat infection. Therefore, serious infections are more likely to develop. Depending on the type and site of infection which develops, the symptoms can vary greatly.

O tempo necessário para desenvolver esses sintomas após o início da doença varia. Normalmente, é dentro de semanas para LLA ou LMA. Pode levar meses ou anos para que os sintomas se desenvolvam com LLC ou LMC, pois essas leucemias progridem lentamente.

The abnormal cells may also build up in lymph glands and in the spleen. You may therefore develop swollen glands in various parts of the body, and develop an enlarged spleen.

Other symptoms which may develop include pain in the bones or joints (mainly with ALL), persistent raised temperature (fever), e perda de peso.

Um exame de sangue

A blood test can often suggest the diagnosis of leukaemia, as abnormal cells are often detected in the blood test. Further tests are usually done to confirm the diagnosis.

Uma amostra de medula óssea

For this test, a small amount of bone marrow is removed by inserting a needle into the pelvic bone (or sometimes the breastbone (sternum)). Local anaesthetic is used to numb the area. A small sample of bone may also be taken. The samples are put under the microscope to look for abnormal cells and are also tested in other ways. This can confirm the diagnosis. (See the separate leaflet called Bone Marrow Biopsy and Aspiration for more detail.) A bone marrow test may not be needed to confirm the diagnosis of CLL.

Análise de células e cromossomos

Testes detalhados são frequentemente realizados em células anormais obtidas da amostra de medula óssea ou do exame de sangue. Estes identificam o tipo ou subtipo exato da célula que é anormal.

Punção lombar

This test collects a small amount of fluid from around the spinal cord - cerebrospinal fluid (CSF). It is done by inserting a needle between the bones (vertebrae) in the lower (lumbar) region of the back. (See the separate leaflet called Lumbar Puncture (Spinal Tap) for more detail.) By examining the fluid for leukaemia cells, it helps to find out if the leukaemia has spread to the brain and spinal cord. This is mainly done when assessing ALL and sometimes AML.

Various other tests

Um raio-X de tórax, blood tests and other tests are usually done to assess your general well-being.

The treatment advised depends on the exact type of leukaemia and on the stage it is at. For example, ALL is usually treated as soon as possible with intensive chemotherapy. On the other hand, people in the early stages of CLL may not need any treatment. This is because CLL often progresses very slowly and may not need treatment for several years.

For details of treatments for each type of leukaemia, read more about:

• Acute lymphoblastic leukaemia.

• Acute myeloid leukaemia.

• Chronic lymphocytic leukaemia.

• Chronic myeloid leukaemia.

The outlook (prognosis) varies for each of the different leukaemias. However, the overall outlook may be better than many people imagine. For example, the outlook for ALL has greatly improved over the period of 20 years or so. Most children with ALL can now be cured.

Also, the chronic leukaemias (CLL and CML) often progress slowly - often over several years. Even in those cases which are not cured, treatment with chemotherapy and other treatments can often prolong survival for quite some time.

Some chemotherapy medicines can affect fertility in both men and women. Sometimes this is temporary and sometimes it is permanent. There is also a very small risk that some medicines used to treat leukaemia may cause another form of cancer much later in your life.

The treatment of cancer and leukaemia is a developing area of medicine. New treatments continue to be developed and the information on outlook above is very general. There are some newer medicines that have been introduced in the last few years that show promise to improve the outlook. The specialist who knows your case can give more accurate information about the treatment and outlook for your particular situation.