Chronic myeloid leukaemia (CML) occurs when too many neutrophils develop from immature cells of the myeloid line of white blood cells.
The disease occurs mainly in adults and rarely in children, and is most commonly associated with a chromosomal abnormality called the Philadelphia chromosome. This rearrangement changes the position and function of certain genes, resulting in uncontrolled cell growth. Other chromosomal abnormalities may also be present.
CML is characterised by a chronic phase that can last for months or years. The disease may have few or no symptoms during the chronic phase. Eventually, however, patients progress from the chronic phase to a more dangerous 'accelerated phase' in which the leukaemia cells grow more rapidly.
Symptoms of chronic myeloid leukaemia (CML)
Many people have no symptoms in the early stages of CML. Instead, the leukaemia is found during routine blood tests. When people do have symptoms of CML, the following are the most common. However, each person's symptoms may be different.
Symptoms may include
·Pain in bones and joints
The symptoms of chronic myeloid leukaemia may be similar to other blood disorders or medical problems. Always check with your doctor for a diagnosis.
Risk factors for chronic myeloid leukaemia (CML)
Possible risk factors include
·Exposure to radiation, chemicals such as benzene
·Non-hereditary genetic mutation
Most people with CML have a genetic mutation called the Philadelphia chromosome.
Every cell in the body contains DNA, which determines how the cell will look and behave. DNA is contained in chromosomes. In CML, part of the DNA moves from one chromosome to another. This change is called a 'Philadelphia chromosome'. It causes the bone marrow to make an enzyme called tyrosine kinase, which causes too many stem cells to develop into white blood cells (granulocytes or blasts).
Philadelphia chromosome occurs when a piece of chromosome 9 and a piece of chromosome 22 break off and swap places. The BCR-ABL gene is formed on chromosome 22, where the piece of chromosome 9 is attached. The altered chromosome 22 is called the Philadelphia chromosome.
The Philadelphia chromosome is not passed from parent to child.
Diagnosing chronic myeloid leukaemia (CML)
A number of tests and procedures may be used to diagnose CML, including
·Bone marrow aspiration and biopsy
·FISH for BCRABL
Additional blood tests and other investigations may also be carried out.
Staging of chronic myeloid leukaemia (CML)
Instead of stages, doctors describe CML in terms of phases: chronic phase, accelerated phase and blast phase.
In this phase, you have less than 10% blasts, which are immature white blood cells, in your blood or bone marrow. You usually have relatively mild symptoms (if any) and respond to standard treatments.
In this phase, you have more than 10% but less than 20% blasts, which are immature white blood cells. You may have a fever, loss of appetite and weight loss. During this phase, your symptoms and blood counts may not respond as well to treatment. Your leukaemia cells may have developed other chromosomal changes in addition to the Philadelphia chromosome (a chromosomal abnormality associated with CML).
During this phase, you have more than 20% of immature blast cells in your blood or bone marrow. These blast cells often spread outside the bone marrow to other parts of the body. If tiredness, fever and an enlarged spleen occur during the blast phase, it is called a blast crisis. This phase is called aggressive.
Treatment for chronic myeloid leukaemia
There are several types of treatment available for people with chronic myeloid leukaemia (CML). Some treatments are standard (currently used) and some are being tested in clinical trials.
Targeted therapies can attack cancer cells without affecting healthy tissue, unlike radiation and chemotherapy.
Tyrosine kinase inhibitors are targeted therapies used to treat chronic myeloid leukaemia.
Imatinib mesylate, nilotinib and dasatinib are tyrosine kinase inhibitors that can be used as initial treatment for newly diagnosed patients with chronic phase CML.
The use of anti-cancer drugs to shrink or kill cancer cells and reduce the spread of cancer to other parts of the body.
Interferon chemotherapy is a mainstay of treatment for CML, especially in older patients. Other chemotherapy drugs, such as hydroxyurea and busulfan, are also often considered.