Table of ContentsView AllTable of ContentsCausesRisk FactorsHow Common Is CML?SymptomsDiagnosisPhasesPrognosisTreatment
Table of ContentsView All
View All
Table of Contents
Causes
Risk Factors
How Common Is CML?
Symptoms
Diagnosis
Phases
Prognosis
Treatment
Chronic myeloid leukemia (CML) is a chronic type of leukemia (cancer of the blood cells) that tends to grow and progress slowly.It is a type of myelogenous leukemia that starts inmyeloid cells, which are a type of immature white blood cell (WBC).
CML is one of the four major categories ofleukemia. The other three are acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), andchronic lymphocytic leukemia (CLL).
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All leukemias begin in the blood-forming cells in the bone marrow. Each type of leukemia is named based on how fast the cancer tends to grow (acute cancer grows fast; chronic grows slowly) as well as the type of blood-forming cells from which the malignancy developed.
This article will discuss the causes, risk factors, and symptoms of CML. It will then cover the process of diagnosing and treating CML.
What Are the Causes of CML?
Certain changes in DNA can cause normal bone marrow cells to become leukemia cells.
People with CML generally havethe Philadelphia chromosome, which contains the abnormal BCR-ABL gene. The BCR-ABL gene causes white blood cells to grow in an abnormal, uncontrolled way, leading to leukemia.
Who Gets Chronic Myeloid Leukemia?
CML can occur at any age, but it is more common in adults over the age of 65, who account for nearly half of all cases.
CML is relatively rare. The American Cancer Society estimates that for the year 2024, about 9,280 new cases will be diagnosed, and there will be about 1,280 deaths. About one in 526 people in the U.S. will get CML at some point in their lifetime.
What Are the Symptoms of CML?
Because CML is a slow-growing cancer, many people do not havesymptomsat the time of diagnosis. Some with leukemia do not have any symptoms at all and arediagnosedbased on abnormalities detected with routine blood work.
CML may cause symptoms as it progresses with time.
The most common symptoms include:
How Chronic Myeloid Leukemia Is Diagnosed
When you are being evaluated for possible leukemia, your healthcare provider will take your medical history and do a physical exam. And you would have many of these same preliminary diagnostic steps even if you are getting a routine medical checkup. Along with an enlarged spleen size, lab, gene, and imaging tests can accurately detect CML.
Spleen Size
Normally, your spleen can’t be felt on a physical exam, but an enlarged spleen can be detected during a physical exam. It can cause a fullness on the left side of the upper abdomen, beneath the edge of the rib cage.
Lab Tests
Too many WBCs and abnormal levels of certain chemicals in the blood may be indicative of CML. These are often described as blasts (immature WBCs) based on their appearance.
If your blood tests are consistent with CML, you may need to have a bone marrow aspiration. This involves a procedure in which a needle is inserted deep into your bone to collect a sample of blood cells. The sample is examined with a microscope.In CML, excess blood-forming cells are present and the marrow is described as hypercellular.
Gene Tests
Gene testing will also be done to see if you have the Philadelphia chromosome and/or the BCR-ABL gene. If you do not have the Philadelphia chromosome or the BCR-ABL gene, then you may have another type of cancer, but it isn’t CML.
Imaging Tests
Diagnostic imaging tests are not needed to diagnose CML. However, they might be performed as part of the assessment of certain symptoms or to evaluate abdominal swelling.
What Are the Three Stages of CML?
CML can be classified into three different phases. The phase is based on the number of blasts in your blood and bone marrow. Knowing the phase of your CML can help you get a sense of how your illness will affect you in the future.
Chronic Phase
In the first phase of CML, you would have an increased number of WBCs in the blood and/or bone marrow. However, blasts should still make up less than 10% of cells.
Usually, in the chronic phase, there are no symptoms, but there can be some fullness of the upper left abdominal area. Your immune system should still be functioning pretty well in the chronic phase, so you can put up a good fight against infections. A person can be in the chronic phase for as short as a few months to as long as many, many years.
Accelerated Phase
In the accelerated phase, the number of blasts in the blood and/or bone marrow is higher than in the chronic phase. Symptoms may include fever, weight loss, decreased appetite, and an enlarged spleen.
The number of WBCs is higher than normal and you can have other changes in your blood counts, such as a high number of basophils (a type of WBC) or a low number of platelets.
There are different sets of criteria used to define the accelerated phase. The World Health Organization (WHO) defines the accelerated phase as the presence of any of the following:
Blast Phase
This phase is often referred to as blast crisis. It is the third and final stage and has the potential to be life-threatening. The number of blasts in the blood and/or bone marrow becomes very high and they can spread to other tissues. Symptoms are much more common in the blast phase and may include infections, bleeding, abdominal pain, and bone pain.
In the blast phase,CML may appear more like AML(acute myeloid leukemia) or ALL (acute lymphoblastic leukemia) than chronic leukemia.
The WHO defines the blast phase as greater than 20% blast cells in the bloodstream or bone marrow. The definition also includes the presence of blast cells outside of the blood or bone marrow.
Chronic Myeloid Leukemia Prognosis
The phase of your CML is an important factor in your prognosis, but it’s not the only factor.
Your age, the size of your spleen, and your blood counts are also used to place you in one of three categories: low, intermediate, or high-risk.
People in the same risk group are more likely to respond in a similar way to treatment. People in the low-risk group generally respond better to treatment. However, these groupings are tools, not absolute indicators.
How Is CML Treated?
With the introduction of tyrosine kinase inhibitor medications in 2001, many people with CML have done very well, and the disease can often be kept in the chronic phase for years.
Still, a number of challenges remain: it can be difficult to predict, from the start, which patients with CML are likely to have poor outcomes. Additionally, most patients need to take tyrosine kinase inhibitors indefinitely, and suppressive treatments are not without side effects.
Some clinical trials have been looking at discontinuing tyrosine kinase inhibitor therapy in people with a deep and long-lasting response to treatment. About half of the patients have been able to stop the medications successfully. People who’ve gone off tyrosine kinase inhibitors can restart the therapy if CML comes back.
Advances in CML treatment have been significant in recent decades, but there is still room for further improvement.
Tyrosine Kinase Inhibitor Therapy
Tyrosine kinase inhibitor therapy is a type of targeted therapy that inhibits the action of the abnormal BCR-ABL gene. These drugs come in the form of pills that can be swallowed.
Immunotherapy
Interferon is a substance that the immune system naturally makes. PEG (pegylated) interferon is a long-acting form of interferon.
Interferon is not used as an initial treatment for CML, but for some patients, this may be an option when they are unable to tolerate tyrosine kinase inhibitor therapy. Interferon comes as a liquid that is injected under the skin or into a muscle with a needle.
Chemotherapy
Omacetaxine is achemotherapydrug used for treating CML that’s resistant to other treatments and/or if you have an intolerance to two or more tyrosine kinase inhibitors. Resistance is when CML does not respond to a treatment or if the disease responds at first but then stops responding. Intolerance is when treatment with a drug must be stopped due to severe side effects.
Omacetaxine is given as a liquid that is injected under the skin with a needle. Other chemotherapy drugs may be injected into a vein or may be given as a pill to swallow.
Hematopoietic Cell Transplant (HCT)
An HCT is a procedure that replaces cells in your bone marrow with new, healthy blood-forming cells.High-dose chemotherapy is used before the procedure to destroy both normal cells and CML cells in the bone marrow.
An allogeneic HCT is a complex treatment and can cause very serious side effects. It is usually considered as a treatment option for patients younger than 65 years of age.
Clinical Trials: Investigational Therapies
New drugs for the treatment of CML are continuously being investigated. Clinical trials may be an option for some patients. You can ask your treatment team if there is an open clinical trial that you can join and whether or not they believe you would be a good candidate for such a clinical trial.
Summary
Chronic myeloid leukemia (CML) is a chronic type of leukemia (cancer of the blood cells) that tends to grow and progress slowly. People with CML may not experience any symptoms. A diagnosis is usually made from a physical exam looking for an enlarged spleen, lab tests, gene tests, and sometimes imaging tests.
Your CML prognosis depends on factors such as your age, disease phase, the number of blasts in your blood or bone marrow, the size of your spleen at diagnosis, and your overall health. With tyrosine kinase inhibitor medications, the disease can often be kept in the chronic phase for years.
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