Chronic Lymphocytic Leukemia

Chronic lymphocytic leukemia (CLL) is a type of blood cancer. It’s the most common form of leukemia in adults. It happens when healthy white blood cells (lymphocytes) in your bone marrow mutate, or change, into cancerous cells that multiply and crowd out healthy blood cells and platelets.

CLL typically affects people aged 65 and older, but it can affect people starting at age 30. You can have chronic lymphocytic leukemia without having symptoms. Most people learn they have CLL after having blood tests as part of routine physical examinations.

Currently, healthcare providers don’t have routine treatments to cure chronic lymphocytic leukemia. During the past 10 years, providers have developed treatments that put CLL into remission. (Remission means you don’t have symptoms and signs of CLL.) These treatments are helping people with CLL live longer.

Types of chronic lymphocytic leukemia

You may develop CLL in your B-cells or T-cells, which are white blood cells (lymphocytes):

• B lymphocytes (B-cells) make antibodies. Antibodies are proteins that target viruses, bacteria and cancer cells, among other foreign intruders.
• T lymphocytes (T-cells) control your body’s immune system response. T-cells directly attack and destroy abnormal cells, including cancer cells.

Nearly all people with CLL have B-cell chronic lymphocytic leukemia. There’s a related condition that affects T-cells called T-cell prolymphocytic leukemia (PLL). People with T-cell PLL develop symptoms more quickly than people who have B-cell CLL.

How common is this condition?

Chronic lymphocytic leukemia is one of the most common types of leukemia in adults. It affects about 5 in 100,000 people in the U.S. The American Cancer Society estimates about 18,700 people will be diagnosed with CLL in 2023. By comparison, more than 238,000 people will be diagnosed with lung cancer in 2023 (one of the most common cancers overall).