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Leukemia: the basics
Leukemia is the general name for four different types of blood cancers. The ways that individuals with leukemia are affected
and treated and the rate at which the disease progresses, are different with each type of leukemia.
What is leukemia?
Leukemia is the general term used to describe four different disease-types called:
* Acute Myelogenous Leukemia (AML)
* Acute Lymphocytic Leukemia (ALL)
* Chronic Myelogenous Leukemia (CML)
* Chronic Lymphocytic Leukemia (CLL)
The terms lymphocytic or lymphoblastic indicate that the cancerous change takes place in a type of marrow cell that forms
lymphocytes. The terms myelogenous or myeloid indicate that the cell change takes place in a type of marrow cell that normally
goes on to form red cells, some types of white cells, and platelets.
Acute lymphocytic leukemia and acute myelogenous leukemia are each composed of blast cells, known as lymphoblasts or myeloblasts.
Acute leukemias progress rapidly without treatment.
Chronic leukemias have few or no blast cells. Chronic lymphocytic leukemia and chronic myelogenous leukemia usually progress
slowly compared to acute leukemias.
Chronic Leukemias
In chronic myelogenous leukemia (CML), the leukemia cell that starts the disease makes blood cells (red cells, white cells
and platelets) that function almost like normal cells. The number of red cells is usually less than normal, resulting in anemia.
But many white cells and sometimes many platelets are still made. Even though the white cells are nearly normal in how they
work, their counts are high and continue to rise. This can cause serious problems if the patient does not get treatment. If
untreated, the white cell count can rise so high that blood flow slows down and anemia becomes severe.
In chronic lymphocytic leukemia (CLL), the leukemia cell that starts the disease makes too many lymphocytes that do not
function. These cells replace normal cells in the marrow and lymph nodes. They interfere with the work of normal lymphocytes,
which weakens the patient's immune response. The high number of leukemia cells in the marrow may crowd out normal blood-forming
cells and lead to a low red cell count (anemia). A very high number of leukemia cells building up in the marrow also can lead
to low neutrophil and platelet counts.
Unlike the other three types of leukemia, some patients with CLL may have disease that does not progress for a long time.
Some people with CLL have such slight changes that they remain in good health and do not need treatment for long periods of
time. Most patients require treatment at the time of diagnosis or soon after.
Chronic Myelogenous Leukemia
Understanding CML
About 4,570 people in the United States will learn they have chronic myelogenous leukemia (CML) in 2007.About 21,501 people
in the United States are living with CML (SEER, National Cancer Institute, 2007). The progress that has been made in treating
CML gives patients more hope than ever before.
Leukemia is a type of cancer. There are four main types of leukemia. CML is one of the four types. CML starts with a change
to a single stem cell. Both children and adults can get CML, but most CML patients are adults.
CML patients have what is called the "Philadelphia Chromosome" (Ph chromosome). Every cell with a nucleus has
chromosomes. The Ph chromosome is made as the result of a piece of chromosome 22 breaking off. With CML, there is a switch
in pieces of chromosome 9 and 22. The break on chromosome 9 involves a gene called "ABL." The break on chromosome
22 involves a gene called "BCR."
A piece of chromosome 9 attaches to the end of chromosome 22 and the BCR-ABL cancer gene is made. The BCR-ABL cancer gene
gives the cell instructions to make a protein that leads to CML.
Causes and Risk Factors
Doctors are working to understand the changes that lead to the Ph chromosome and the BCR-ABL cancer gene. Some risk factors
that may cause these changes are:
* Very high levels of radiation (such as atomic bomb survivors were exposed to in World War II)
* High dose radiation therapy used to treat other cancers.
Most people with CML do not have these risk factors. Many people with these risk factors do not get CML. There is no link
between dental or medical x-rays and increased risk of CML. You cannot catch CML from someone else.
Signs and Symptoms
CML signs and symptoms tend to develop slowly. Some patients learn about their CML after a routine blood test given during
a check up.
Some changes that a person with CML may have are:
*
Tiredness
*
Shortness of breath doing activities
*
Pale-looking skin
*
Enlarged spleen
*
Night sweats
*
Weight loss
These signs and symptoms for CML are common to other illnesses.
Phases of CML
CML can have three phases:
* The chronic phase
* The accelerated phase
* The blast crisis phase
Most patients are in the chronic phase of the disease when their CML is found. During this phase, CML symptoms are less
intense. White cells can still fight infection. Once patients in the chronic phase are treated, red cells and platelets can
do their jobs. Most patients can go back to their usual activities.
In the accelerated phase, the patient may develop anemia, the number of white cells may go up or down or the number of
platelets may drop.
The number of blast cells increases. The spleen may swell and the patient may feel ill.
During the blast crisis phase:
* The number of blast cells increases in the marrow and blood
* The number of red cells and platelets drops
* The patient may have infections
* The patient may be tired and have shortness of breath, stomach pain, bone pain or bleeding.
CML patients begin treatment with a drug called Gleevec. This drug has been FDA-approved since 2001. For some patients,
Gleevec keeps CML under control for as long as they take the drug. Some patients taking Gleevec have strong side effects or
the drug does not work for them. Patients who do not respond to the usual dose of Gleevec may do better with a higher dose.
For other patients, there are two newer drugs called Sprycel and Tasigna. These drugs also block the BCR-ABL cancer gene.
They work in a different way than Gleevec. All three of these drugs are taken by mouth.
Most patients being treated for chronic phase CML can go about their day-to-day activities. With drug treatment most patients
are symptom free for very long periods (called a remission).
However, patients are not cured of CML with drug treatment. They are checked carefully for any signs that CML is returning
(called a relapse). They will need regular health check-ups, including blood tests. From time to time a patient will need
a bone marrow test.
CML is likely to return if drug treatment is stopped. The disease may also return if the drug treatment stops working
(called drug resistance). There are other drug treatments for patients who develop resistance to a particular drug.
Leukapheresis
Some patients have very high white cell counts at the time the doctor discovers their CML. This can reduce blood flow
to the brain, lungs, eyes and other places in the body. Patients can have white cells removed by a machine. The process is
called leukapheresis. A drug called hydroxyurea (Hydreaź) may also be used to decrease the white cell count. After the white
cell count drops, Gleevec can be started. Leukapheresis can be used for patients diagnosed with CML in the first months of
pregnancy, when drug therapy may be harmful to the unborn baby.
Accelerated Phase or Blast Crisis Phase Treatment
The goal in treating accelerated or blast crisis phase CML is to kill all cells that contain the BCR-ABL gene or to return
the patient's disease to the chronic phase.
Gleevec, and for certain patients, Sprycel, are important treatments for accelerated or blast crisis phase CML. Stem cell
transplantation is another important treatment for certain patients.
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