The distinction affects which treatment you choose—if you need treatment at all.
Blood cancer comes in many forms, each with unique characteristics, prognoses, and treatment options. Leukemia is a type of blood cancer (along with myeloma and lymphoma) that starts in the stem cells (early blood cells) of the bone marrow, according to Sangmin Lee, MD, hematologist-oncologist at Weill Cornell Medicine and NewYork-Presbyterian Hospital.
Leukemia cells multiply faster than your normal stem cells (which are immature blood cells that eventually mature to red and white blood cells and platelets). Leukemia cells do not function like blood cells, and they block those blood cells from multiplying, according to the Leukemia and Lymphoma Society.
Because of this, leukemia cells crowd out your normal blood cells and can deprive you of healthy blood functioning. For example, someone with advanced leukemia may easily get infections due to low levels of normal, healthy white blood cells, which are part of the immune system.
Leukemia can be divided into additional subtypes, depending on which blood cells are affected (myeloid or lymphocytic) and how quickly the leukemia is progressing (acute or chronic). Learn more about the four main types of leukemia here.
“In your bone marrow, you typically start out with young blood cells … that mature into more mature [blood cells], such as your white blood cells, hemoglobin, and platelets,” says Dr. Lee. “The difference between acute and chronic leukemia depends on typically where [the cells are] affected in the maturation process.”
Acute leukemia means the cancer is progressing rapidly—and can thus be harder to treat. In acute leukemia, the affected cells are still immature and cannot mature at all, and thus are not able to maintain any of their normal function. This makes acute leukemia more likely to cause symptoms of leukemia.
Chronic leukemia means the cancer is progressing more slowly. In fact, it may take years to develop, and the individual may never experience symptoms. Instead, people with chronic leukemia are often diagnosed during routine blood tests (which may reveal abnormal blood cell counts).
Unlike with acute leukemia, the blood cells in chronic leukemia are actually partially mature, so even though they are cancer cells, they may still be able to maintain some normal function (and thus cause fewer and less severe symptoms and complications).
Knowing whether you have acute or chronic leukemia is important for deciding the right course of treatment. Because acute leukemia moves rapidly, it usually requires more aggressive treatment options, such as targeted therapy for leukemia.
On the other hand, treatment for chronic leukemia is much less urgent. In fact, it may not even need treatment at first, and doctors may use a “watch and wait” method.
Treatment for leukemia is undergoing rapid change, according to Dr. Lee. “We have many more targeted therapies and immunotherapies [for leukemia] that were not available many years ago, so treatment for leukemia is constantly improving,” says Dr. Lee.
Leukemia. Atlanta, GA: American Cancer Society. (Accessed on June 11, 2019 at https://www.cancer.org/cancer/leukemia.html.)
Leukemia. Rye Brook, NY: Leukemia & Lymphoma Society. (Accessed on June 11, 2019 at https://www.lls.org/leukemia.)
Leukemia—patient version. Bethesda, MD: National Cancer Institute. (Accessed on June 11, 2019 at https://www.cancer.gov/types/leukemia.)
What is chronic myeloid leukemia? Atlanta, GA: American Cancer Society, 2018. (Accessed on June 11, 2019 at https://www.cancer.org/cancer/chronic-myeloid-leukemia/about/what-is-cml.html.)