Chronic lymphocytic leukemia (CLL) is a type of cancer that affects the lymphocytes, a type of white blood cell. CLL begins in the bone marrow and then travels to the blood. Later, it may spread to the lymph nodes and other organs, including the lungs, spleen, and liver.

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This condition is one of the most common types of leukemia in adults. It often starts during or after middle age and rarely affects children. Data from 2014–2018 suggest that the rate of new cases per year is 4.6 per 100,000 people in the United States.

In this article, we provide an overview of CLL, including its types, symptoms, causes, diagnosis, and treatment. We also look at the outlook for people with this condition.

There are two types of CLL. One type grows slowly, while the other grows more rapidly and is more serious.

The leukemia cells of the two types look alike, but those of the slower growing type have low amounts of proteins called CD38 and ZAP-70. Low levels of these proteins generally cause the cancer to grow more slowly. Doctors can check for these proteins to get an idea of a person’s outlook, which will likely be better if the cancer is slow to progress.

The symptoms of CLL can vary from mild to severe, and some individuals may have more symptoms than others. The most common symptoms include:

  • enlarged lymph nodes
  • fatigue
  • fever
  • enlarged liver, spleen, or both
  • night sweats
  • weight loss
  • frequent infections
  • loss of appetite
  • abnormal bruising

Possible complications of CLL include:

  • a higher risk of infections
  • low blood cell counts
  • a higher risk of a second cancer

Doctors do not know the cause of CLL. However, about 10% of people with CLL have a family history of the condition.

Risk factors for CLL include:

  • Age: The risk increases with age. Of those with the condition, 9 in 10 are over the age of 50 years.
  • Family history: People who have parents, children, or siblings with the cancer have more than double the risk of developing CLL.
  • Exposure to certain chemicals: Some research links CLL to exposure to Agent Orange, a herbicide that the military used during the Vietnam War. Other studies suggest that long-term exposure to some pesticides may increase the risk of developing CLL.
  • Sex: This leukemia is slightly more common in males than in females.
  • Race and ethnicity: This leukemia is more prevalent in Europe and North America than in Asia. As Asian people living in the U.S. have the same risk as those living in Asia, experts believe that the risk factor is genetic rather than environmental.

Doctors may use a range of tests to diagnose CLL, including:

  • Health history and physical exam: A doctor will ask a person about their health conditions and treatments. They will also check for signs of the cancer, such as enlarged lymph nodes.
  • Complete blood count test: This test measures the number of red blood cells and platelets, which are the cell fragments involved in blood clotting. It also measures the number and types of white blood cells and the amount of hemoglobin, which is a protein in red blood cells that carries oxygen.
  • Blood chemistry studies: These measure certain substances that tissues and organs release into the blood. A lower or higher amount may be a sign of leukemia.
  • Beta-2-microglobulin testing: This test measures a small protein present on the surface of various cells, including lymphocytes. A higher amount may indicate some types of cancer.
  • Lactate dehydrogenase testing: Doctors use this to measure one of a group of enzymes in the blood. A higher amount may suggest tissue damage and cancer.
  • Flow cytometry: Flow cytometry measures the number of cells in a sample and their characteristics, such as shape, size, and the presence of tumor markers.
  • Gene mutation testing: Doctors can look for changes in certain genes to get an idea of a person’s likely outlook.
  • Fluorescence in situ hybridization (FISH): FISH counts chromosomes or genes in cells and tissues, which helps a doctor diagnose cancer and decide on the best treatment approach.
  • Serum immunoglobulin testing: This test measures specific blood antibodies. It helps diagnose cancer and shows whether treatment is effective.

Doctors can treat CLL in a range of different ways, some of which are more common than others.

Most common treatments

The treatments that doctors are more likely to recommend include:


Chemotherapy attacks fast growing cells, including cancer cells. The main types of chemotherapy for this condition are purine analogs and alkylating agents. Purine analogs, also called antimetabolites, prevent cells from reproducing, while alkylating agents prevent cells from making copies of themselves.

Monoclonal antibodies

Monoclonal antibodies are synthetic versions of immune system proteins that help the immune system attack cancer by binding to proteins on cancer cells. A standard treatment for CLL is a combination of chemotherapy with monoclonal antibodies.

Targeted therapy

These medications target specific changes in cells that cause them to turn into cancer. Doctors often include this therapy in first-line treatment for CLL.

Supportive care

Aside from treatment to remove cancer, an individual may need supportive care, which can address problems related to medications and the effects of cancer. Supportive care can include treatment to prevent infections, such as antibiotics and vaccines. It may also involve interventions to remedy low blood counts, such as blood transfusions.

Stem cell transplants

A stem cell transplant involves receiving higher dosages of chemotherapy and possibly radiation therapy to treat the cancer. Afterward, a person receives the transplant to restore bone marrow. Doctors do not yet know how beneficial stem cell transplants are for this type of cancer.

Less common treatments

Other treatment options include:


Although doctors rarely use leukapheresis, they may recommend it when someone has very high numbers of white blood cells. The treatment involves removing the blood through an intravenous (IV) line and putting it back through another IV line.


As leukemia cells spread widely, doctors do not use surgery very often. However, they sometimes use minor surgery to remove a lymph node for diagnosis. In rare cases, they may remove the spleen, as CLL can cause it to grow and push on other organs, which can cause problems.

Radiation therapy

This treatment uses high energy rays to destroy cancer cells. Doctors rarely include this in the main treatment of CLL, but they do use it in some instances.

When a doctor finds no signs of cancer following treatment, this is called complete remission. However, at some point, the cancer will likely appear again.

The relative 5-year survival for people with this leukemia for 2011–2017 was 86.9%, showing that most people with CLL will live for at least 5 years after their diagnosis compared with people without the condition. This estimate does not include deaths from other causes.

Although CLL is rarely curable, most people with the condition live with it for many years. As a consequence, most individuals receive treatment on and off for an extended period.

It is important that people go to all follow-up appointments so that doctors can monitor their condition before, during, and after treatment. Some people may also wish to ask their doctor for a survivorship care plan, which may include:

  • a schedule for follow-up tests and exams
  • a list of possible late side effects of treatment
  • diet and exercise recommendations

After the end of treatment, an individual should maintain their health insurance because they may need further treatment at a later date. A person should also keep medical records up to date in case they need to see a new doctor who is unfamiliar with their medical history.

Although doctors do not know for sure whether healthy lifestyle practices can reduce the risk of cancer recurrence, taking the following steps may help:

  • quitting smoking, if applicable
  • eating a healthy diet
  • exercising regularly
  • aiming for a healthy weight

Lastly, symptoms of depression and anxiety are normal with this condition, so it is beneficial to seek support from family, friends, and professional counselors.

Chronic lymphocytic leukemia may cause various signs and symptoms, such as enlarged lymph nodes, fever, and tiredness. The cause remains unknown, but risk factors include being an older adult and having a family history of the condition.

The standard treatment consists of a combination of chemotherapy and monoclonal antibodies. The outlook for people with CLL is generally good compared with other cancers, with the disease having a relative 5-year survival rate of about 86.9% for people of all ages.