Leukaemia is an umbrella term encompassing cancers that affect the blood and the body's blood-forming tissues. Chronic myeloid leukaemia (CML) is a slowly developing form of the disease that primarily affects individuals over the age of 55.
Like all types of leukaemia, CML originates from issues in the process of blood cell creation.
The body produces millions of blood cells daily, mostly within the bone marrow, the spongy tissue inside bones that houses immature stem cells. In a healthy person, these immature stem cells develop into either lymphoid stem cells or myeloid stem cells.
Lymphoid stem cells mature into white blood cells, which are part of the immune system. They initially become lymphoblasts, then mature into lymphocytes (B cells and T cells). B cells produce antibodies to combat bacteria and viruses, while T cells help signal other immune cells or directly fight infection.
Myeloid stem cells also develop into white blood cells. They first become myeloblasts, which then mature into monocytes and granulocytes (including neutrophils), all vital for fighting disease. Other myeloid stem cells form red blood cells (which transport oxygen) and platelets (essential for blood clotting).
Leukaemia occurs when the DNA (the genetic instructions controlling cell activity) of a bone marrow stem cell mutates. The cell turns cancerous, begins to multiply rapidly, and overcrowds the healthy cells in the blood and bone marrow. These diseased cells may also accumulate in various organs, such as the liver, lymph nodes, spleen, and skin.
Leukaemia is typically classified based on the type of stem cell that became cancerous (lymphoid or myeloid) and whether the disease is chronic or acute.
Acute leukaemia affects immature cells, preventing them from developing and functioning correctly. These cells tend to multiply quickly, making acute leukaemia more aggressive.
Chronic leukaemia involves mature or partially mature cells. These cells multiply more slowly and are less aggressive than those in acute leukaemia.
CML develops from myeloid stem cells, which are responsible for producing red blood cells, platelets, and several types of white blood cells known as granulocytes. In patients with CML, an excessive number of myeloid cells become granulocytes. These cancerous cells are ineffective at fighting disease and crowd out healthy blood cells, often causing patients to feel weak and be prone to infection.
CML predominantly affects older patients, with approximately half of all cases diagnosed in people aged 65 and above. It is very uncommon in paediatric patients.
Nearly all CML patients possess a specific chromosome abnormality known as the Philadelphia chromosome. Chromosomes are sections of DNA found in every cell. The Philadelphia chromosome is formed when sections of chromosomes 9 and 22 swap places within a blood cell. This genetic change causes the cancerous cell to produce a protein (from the tyrosine kinase family) that encourages it to multiply rapidly.
A risk factor is anything that increases the likelihood of developing a disease, though having risk factors does not guarantee that a person will develop CML. Risk factors for CML include:
The majority of CML cases are found in people aged 65 or older.
Men are more likely to develop CML than women.
Exposure to high levels of radiation, such as that from nuclear bombs, is a risk factor. However, radiation therapy used for cancer treatment is not considered a risk factor for CML.
While there are various types of leukaemia, their symptoms can often be similar. Since chronic leukaemia develops slowly, CML patients may not experience symptoms for months or even years. In such instances, the disease is often discovered incidentally during a routine blood test performed for an annual physical or another medical reason.
When CML patients do develop symptoms, they are often a result of a lack of properly functioning blood cells needed to transport oxygen, combat infection, and stop bleeding. Low levels of haemoglobin (the oxygen-carrying protein) can also contribute to symptoms.
Weakness, tiredness, and fatigue, which may be caused by the leukaemia itself or low haemoglobin levels.
Fever and frequent infections due to low counts of healthy white blood cells.
Excessive sweating, particularly at night.
Easy bleeding and bruising, including bleeding of the gums, caused by low platelet levels.
Recurrent nosebleeds.
Petechiae: a rash-like collection of tiny, pinpoint spots on the skin due to bleeding into the skin, also a result of low platelet levels.
Shortness of breath, which may be due to low haemoglobin levels or lung infections.
Swollen lymph nodes in the neck, underarm, stomach, or groin area.
Loss of appetite or feeling full after consuming very little food, caused by an enlarged spleen.
Unexplained weight loss.
Bone and joint pain.
For female patients, menstruation that is longer or heavier than normal.
A leukaemia diagnosis typically begins with a simple blood test called a complete blood count (CBC), which a doctor may order after assessing a patient's symptoms or as part of a routine check-up.
If the blood test reveals leukaemia cells or abnormal levels of red blood cells, white blood cells, or platelets, further tests may be ordered to provide a definitive leukaemia diagnosis and determine the extent of the disease. These tests are also used to monitor the disease's progress and track its response to treatment.
At SSCHRC, suspected leukaemia cells are examined by pathologists who specialise exclusively in diagnosing leukaemia and its many subtypes, ensuring an accurate and precise diagnosis, which is the foundation for effective treatment.
For leukaemia, patients typically undergo a bone marrow biopsy. This involves using a needle to take a sample of bone marrow from the hip to check for cancerous cells.
If leukaemia is diagnosed, additional tests can determine if specific chromosomes or gene mutations, or certain proteins or molecules, are present on the diseased cells. This profiling helps doctors determine the patient's exact type of leukaemia and prognosis, as cancers with different genetic features may respond differently to treatments. This information is crucial for developing an optimal treatment plan.
Leukaemia may spread to the central nervous system (the brain and spinal cord). A lumbar puncture is used to examine the patient's spinal fluid for this spread. During the procedure, a small dose of chemotherapy may also be administered into the spinal fluid to target any leukaemia cells present.
Doctors may order imaging scans to look for the presence of cancer in various parts of the body.
CML is not described by stages (which typically indicate how much and where cancer has spread), but rather by phases. These phases are defined by the percentage of immature blood cells, known as blasts, found in the blood and bone marrow.
Fewer than 10% of the cells in the blood and bone marrow are blast cells.
10% to 19% of the cells in the blood and bone marrow are blast cells.
20% or more of the cells in the blood or bone marrow are blast cells. When this phase is accompanied by tiredness, fever, and an enlarged spleen, it is referred to as a blast crisis.
The goal of leukaemia treatment is to achieve remission and ultimately cure the patient. For leukaemia, complete remission generally means that a patient's bone marrow shows no detectable microscopic evidence of the disease, and their blood counts have returned to normal. Patients who maintain complete remission for an extended period, typically measured in years, are considered cured, indicating an extremely low chance of recurrence.
At SSCHRC, a team of highly experienced specialists communicates and collaborates daily to customise comprehensive leukaemia treatment plans for each patient.
Treatment for CML is adapted according to the disease phase: chronic, accelerated, or blastic.
Patients typically receive targeted therapy. Younger patients may also be candidates for a stem cell transplant. Chemotherapy may also be given to help lower elevated white blood cell counts.
A stem cell transplant, targeted therapy, and chemotherapy are the primary treatment modalities.
Targeted therapy drugs are designed to interfere with specific molecules (often proteins) that cancer cells need to survive, multiply, and spread. For CML, the most common targeted therapy drugs are tyrosine kinase inhibitors (TKIs). These drugs are designed to block the tyrosine kinase protein that promotes the rapid multiplication of cancerous white blood cells. The introduction of TKIs has significantly improved the outlook and extended the survival times for CML patients, with the disease's five-year survival rate now exceeding 70%.
Chemotherapy drugs are used to kill cancer cells, control their growth, or alleviate disease-related symptoms. Treatment may involve a single drug or a combination of multiple drugs, depending on the type and growth rate of the cancer.
A stem cell transplant, also known as a bone marrow transplant, is a procedure that replaces cancerous bone marrow with new, healthy bone marrow stem cells. It is usually performed after an intensive round of chemotherapy designed to eliminate the patient's existing bone marrow cells. This treatment may be necessary for patients whose leukaemia has returned or has not responded to standard treatments, or for those with a high-risk form of leukaemia. Because it can be physically challenging, it is generally reserved for patients who are younger and otherwise healthy.
As a top cancer centre, SSCHRC offers various clinical trials for CML, many of which are unavailable elsewhere. These trials explore new drug combinations and novel drugs, including targeted therapies and immunotherapies, offering patients access to cutting-edge treatments.