Chronic Myeloid Leukemia vs. Chronic Lymphocytic Leukemia: What Are the Differences?

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Chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL) are both persistent forms of leukemia that primarily affect adults. They’re also both slow-growing forms of blood cancer

CLL starts in the bone marrow’s lymphocytes (a specific type of white blood cell). CML starts in the bone marrow’s cells that are the precursors to white and red blood cells and platelets (the cells that aid in blood clotting).

While these two types of leukemia are similar, they also have important differences regarding their diagnoses and treatments. This article will discuss their symptoms, causes, diagnosis, and treatment.

Different Symptoms of Chronic Myeloid Leukemia vs. Chronic Lymphocytic Leukemia - Illustration by Michela Buttignol

Verywell / Michela Buttignol

Symptoms 

CML and CLL share several symptoms, most of which are vague and may be shared by a variety of other conditions. However, they each have some unique symptoms.

Common symptoms of CML and CLL include:

  • Weakness and fatigue
  • Weight loss
  • Fever
  • Night sweats
  • Swollen abdomen or feeling of fullness in the abdomen (due to a swollen liver or spleen)
  • Increased instances of infection
  • Easy bruising or bleeding

Many of these symptoms are due to leukemic cells taking over the bone marrow so the normal white and red blood cells and platelets cannot be made. The leukemic cells do not function as well as normal cells. This results in anemia (low red blood cells), leukopenia (low normal white blood cells), and thrombocytopenia (low blood platelets).

Each condition has some symptoms or signs that are different from the other.

CML
  • Bone pain

  • Abnormal white blood cell count, with immature cells seen

CLL
  • Swollen lymph nodes

  • High lymphocyte count

Causes

In both CLL and CML, experts don’t know the exact cause of the disease. Gene changes likely play a role. Neither form of leukemia is inherited. Instead, the changes responsible for these types of cancers are typically acquired during a person's lifetime.

Experts know that most people with CML have an abnormal chromosome called the Philadelphia chromosome, which is responsible for out-of-control cell growth and division. However, they don’t know exactly why some people have this chromosome.

While experts can't pinpoint the definitive cause for CML and CLL, each disease has known risk factors.

CML Risk Factors

Known risk factors for CML include:

  • Older age
  • Exposure to radiation
  • Being male

CLL Risk Factors

Known risk factors for CLL include:

  • Being over age 50 
  • Chemical exposure to Agent Orange (an herbicide used in the Vietnam War) or radon (a naturally occurring radioactive gas that can accumulate in buildings)
  • Having a family history of the cancer
  • Being male 
  • Being white

Diagnosis 

Neither form of leukemia can be diagnosed during a physical exam. A doctor needs to perform additional tests to confirm a diagnosis of CML or CLL.

CML

Most people with CML don’t display symptoms. Diagnostic testing may involve:

  • Blood tests: A complete blood count (CBC) and peripheral smear can tell doctors whether there are abnormal levels or types of cells. White blood cell counts will be high in people with CML, and there may be abnormal immature cells seen. They may also have low red blood cell counts and high or low platelet counts.
  • Bone marrow biopsy: A bone marrow sample can help with diagnosis (having too many blood-forming cells in the bone marrow is a sign of CML) and let doctors know whether treatment is working. 
  • Genetic testing: The presence of a Philadephia chromosome can help narrow down a diagnosis. In people without the Philadelphia chromosome, polymerase chain reaction (PCR) testing can help detect the BCR-ABL gene associated with CML. 
  • Imaging tests: Computed tomography (CT) scans and ultrasounds help check for lymph node enlargement, which may be a sign of leukemia.

CLL

During your physical, the doctor will ask about your medical and family history. Having a family history of leukemia may increase your odds of developing this type of cancer. Other things the doctor will look for include swollen lymph nodes and swelling in the abdomen.

Tests for CLL may include:

  • Blood tests: A CBC can determine whether you have abnormal blood cell counts that may point to a disease such as leukemia. If you have too many lymphocytes, this may mean you have CLL. 
  • Flow cytometry: This test looks at whether lymphocytes taken during a blood draw contain cancer cells. 
  • Bone marrow biopsy: This test can help with CLL staging.
  • Lymph node biopsy: Removing lymph node tissue and looking at the cells under a microscope gives doctors an idea of the aggressiveness of the cancer.
  • Imaging tests: As with CML, CT scans and ultrasounds can detect enlarged lymph nodes or organs such as the spleen, which may be a sign of leukemia. 
  • Gene testing: These types of tests are not typically used to diagnose CLL but help determine how advanced the cancer is and what to expect in terms of outlook.

Treatment 

A proper diagnosis is vital because the treatments for different types of cancer may not be the same. The first-line treatments for CML and CLL differ.

CML

Doctors typically start by treating those with CML with targeted therapies. Targeted therapies are drugs that work on specific cells. In the case of CML, drugs called tyrosine kinase inhibitors (TKIs) target the abnormal BCR-ABL gene. Targeted drugs are considered a long-term treatment.

Rarely, they may also treat CML with:

  • Chemotherapy (using powerful drugs to kill fast-growing cells, including cancer cells)
  • Radiation therapy (using high-powered radiation to shrink and kill tumors)
  • Surgery
  • Stem cell transplant (sometimes called a bone marrow transplant, replacing damaged stem cells with healthy ones)

Targeted therapies are much more effective, making these treatments less common nowadays.

CLL

Doctors typically recommend chemotherapy, monoclonal antibodies, targeted therapies, or a combination of these as a first-line treatment for CLL. Monoclonal antibodies are synthetic immune system proteins that target specific cells.

They may also treat CLL using stem cell transplants, particularly in the case of hard-to-treat CLL.

Prevention 

Because little is known about what exactly causes either of these cancers, experts don’t know how to prevent them.

However, avoiding exposure to high amounts of radiation or radon can lower your risk of developing CML and CLL, respectively. That said, most people don’t knowingly or purposely expose themselves to these substances.

Summary 

Chronic myeloid leukemia (CML) and chronic lymphocytic leukemia (CLL) have many similarities in their symptoms. It’s essential to get a proper diagnosis because treatment differs for these types of leukemia.

For example, the treatment of choice for CML involves targeted therapy drugs. In contrast, CLL treatment may involve a combination of chemotherapy, targeted therapy, and monoclonal antibodies. 

A Word From Verywell 

If you have either of these types of leukemia, the good news is that they are highly treatable. Both also have a good prognosis. The five-year survival rate for CLL is about 87%. For CML, it’s about 70%.

You can do very little to prevent these types of cancer. But you can visit a doctor if you notice any out-of-the-ordinary symptoms, including a feeling of fullness in your abdomen, swollen lymph nodes, and night sweats. 

Frequently Asked Questions

  • What’s the difference between acute leukemia and chronic leukemia?

    Both CML and CLL are chronic forms of leukemia. That means they’re slow growing. Acute leukemias progress and worsen more rapidly.

  • How do people develop the Philadelphia chromosome that’s responsible for CML?

    This abnormal chromosome results from genetic changes that occur during a person’s lifetime. You don’t inherit this gene. Researchers still don’t know why this gene abnormality happens in some people.

  • What are other types of leukemia aside from CML and CLL?

    Other types of leukemia include hairy cell, promyelocytic, myeloproliferative, and systemic mastocytosis. There is also acute lymphocytic leukemia and acute myeloid leukemia.

  • Can children develop CML or CLL?

    It is possible. However, both cancers are far more likely to occur in adults.

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24 Sources
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