A leukemia type that happens quite rarely is called chronic myelogenous leukemia (CML). Sometimes, it is called an uncommon type of bone marrow cancer. The body part that produces blood cells (including red and white ones) is called the bone marrow. The white blood cells (also called lymphocytes) levels begin to increase in people with CML.
The name of this cancer type such as “chronic” means that it develops slowly compared to acute cancer forms and “myelogenous” refers to the cell type involved in this disease.
In some cases, CML is called chronic myeloid leukemia or chronic granulocytic leukemia and it mostly affects older people. However, it may happen in children or at any age but rarely.
There are multiple treatment options used to treat this cancer type. Moreover, there are a lot of people who get remission and live for many years after being diagnosed with CML.
Symptoms
In the early stages, CML usually does not cause symptoms and can be identified by performing a blood test. When the symptoms occur, they often include the following ones. For example:
- Bone pain
- Bleeding
- A feeling of fullness even after a small meal
- Extreme tiredness (fatigue)
- Fever
- Unusual weight loss
- Loss of appetite
- Pain
- Excessive sweating, especially during sleep
- Bleeding in the back of the eye that may lead to blurred vision or other problems
If any of the symptoms listed above occur, immediately visit your healthcare provider.
Causes
Usually, this cancer type occurs when certain changes to the bone marrow cells happen. Experts do not understand why this process begins but they identified how it progresses into CML.
Development of a New Chromosome
Normally, people have 23 pairs of chromosomes that hold the DNA with instructions that tell cells when to grow, multiply, and die. People with CML have two changed chromosomes, including extra-short chromosome 22 and extra-long chromosome 9. It occurs because a part of the chromosome 9 goes to chromosome 22.
The abnormal chromosome 22 (extra-short) is also called the Philadelphia chromosome. The name comes from the city where it was discovered. Furthermore, in people with CML, the Philadelphia chromosome is present in about 90% of blood cells.
The Philadelphia Chromosome
After that, these abnormal chromosomes make a new one called BCR-ABL. This new gene gives different instructions to the blood cells, which causes an increased production of a protein called tyrosine kinase. Therefore, high levels of this protein cause the cancerous cells to grow and multiply abnormally.
These abnormal blood cells start to grow in the bone marrow. In normal circumstances, the bone marrow makes immature cells (also known as blood stem cells) controllably. Thereafter, these cells mature and specialize into white and red blood cells and platelets in the blood.
However, in people with CML, this process does not work properly, causing increased levels of white blood cells (lymphocytes). Approximately all of these abnormal cells contain the Philadelphia chromosome. Therefore, when the abnormal white blood cells grow and multiply abnormally, they form a mass that may invade healthy tissues and destroy them.
Risk Factors
Check below some factors that may increase your risk of developing chronic myelogenous leukemia:
- Age – This leukemia type occurs mostly in older adults.
- Sex – Men are more prone to develop CML than women.
- Continuous radiation exposure – Radiation therapy (a treatment used to kill cancer cells) is linked with CML.
There are no sure ways to prevent this cancer type because physicians do not fully understand why it happens.
In addition, a family history of CML is not a risk factor because the abnormal gene does not pass from biological parents to biological children. However, experts believe these DNA changes develop after birth.
Diagnosis
First, doctors may evaluate your medical history and ask some questions about the symptoms. However, they will perform some tests to confirm the condition and exclude others that may cause similar symptoms to CML. Check below some tests used to diagnose this leukemia type:
- A physical examination – During this procedure, doctors check for irregularities associated with chronic myelogenous leukemia (including swelling of the lymph nodes, spleen, and abdomen).
- Blood tests – These tests are done to check for white blood cells, which are often high in people with CML. A blood test may also check the function of different organs.
- Bone marrow tests – These include biopsy and aspiration. The samples drawn from these tests are sent to the laboratory for testing.
- The Philadelphia chromosome tests – healthcare professionals may perform additional blood tests to check for this abnormal chromosome present in people with CML. Tests usually include FISH (fluorescence in situ hybridization analysis) and PCR (polymerase chain reaction test).
Once you are diagnosed with this cancer type, doctors may perform additional tests to determine the stage (extent) of the cancer. Staging the cancer helps your doctor make the best treatment plan for you.
Treatment
The treatment goal is to destroy blood cells that contain the abnormal gene (BCR-ABL). In most cases, CML treatment begins with targeted therapy.
Targeted Therapy
This treatment option involves specific medicines that block certain substances in the cancer cells, causing them to die. Generally, the target of the medications is tyrosine kinase protein made by the abnormal gene. Thus, the group of medicines used to treat CML is called tyrosine kinase inhibitors (TKIs). However, these medicines may give you some adverse reactions including swelling, skin puffiness, nausea, muscle cramps, extreme tiredness (fatigue), diarrhea, and skin rashes.
During treatment, doctors may perform blood tests to check for abnormal gene presence. It also helps understand how effective is targeted therapy. Sometimes, people develop resistance to this treatment or even do not respond to treatment. In such cases, doctors may change the medicines or recommend other treatments.
Physicians do not know how long a person should take targeted therapy medicines. That’s why you should take the medications until a blood test shows remission of the cancer.
Bone Marrow Transplant
This is the only treatment option that can cure CML. In any case, physicians often recommend it when other treatments do not work because bone marrow transplant carries an increased risk of life-threatening complications.
Commonly, physicians prescribe high doses of chemotherapy during a bone marrow transplant to destroy abnormal blood-forming cells.
Chemotherapy
This treatment option involves strong medications to destroy cancerous cells throughout the body. Chemotherapy drugs are usually given intravenously, but a pill form also is available. Extreme tiredness (fatigue), infections, hair loss, and appetite changes are the most common adverse reactions caused by this treatment option.
Frequently Asked Questions
Is CML curable?
The only way to cure this cancer type is a bone marrow transplant. However, this treatment is reserved for people who have not been helped by other treatments (including targeted therapy, chemotherapy, and others).
What is the survival rate for chronic myelogenous leukemia?
Generally, the 5-year survival rate for CML is approximately 90%. However, most people get remission of the cancer with targeted therapy only.
What are the complications of chronic myelogenous leukemia?
Complications may occur due to CML as well as from treatments. For example:
- Infections
- Bleeding
- Organ damage that may lead to pancreatitis, hepatomegaly, kidney problems, and others
- Anemia
- Bone pain
This article does not contain a full list of complications. If you have any other questions, ask your healthcare professional.
