What is a Leukemia?

Leukemia from Greek "leukos" & "heima," meaning "white blood"

By:Allan Miller, M.D.

Leukemia is defined as a cancer of blood-forming organs. The main blood-forming organs in the body are the bone marrow, the lymph glands, and the spleen. You can think of the spleen as the body's biggest lymph node. In our blood, we have 3 major cell types:

(1) Red blood cells. They carry oxygen. All of the body's red blood cells are made in the bone marrow. A red blood cell has a lifespan of approximately 120 days, so we produce about 1% of our red blood cells every day. If you want to impress your friends, this is called erythropoiesis.

(2) Platelets. They are also only made in the bone marrow and are responsible for helping the blood to clot. The life span of a normal platelet is 7-10 days.

(3) White blood cells. Approximately 60-70% of white blood cells, known as granulocytes, are produced in the bone marrow and the rest of the white blood cells, known as lymphocytes, are produced in the spleen and lymph nodes. Granulocytes, produced in bone marrow, are our infection-fighting cells. They have a lifespan of 6-8 hours in our circulation.

In defining 'leukemia' we are talking about the change of a normal white blood cell into a "malignant" or "cancerous" white blood cell. There are also leukemia's of red blood cells, termed erythroleukemia and leukemias of platelets termed acute megakaryocytic leukemia, but these are extremely rare.

There are certain age groups of people that tend to develop certain types of leukemia. Quick developing Leukemias that occur in white blood cells created in bone marrow primarily happen in adults. This type of cancer is called Acute Granulocytic (Myeloid) Leukemia (AML). With the advancement in treatments, the 5-year overall survival rate is now 25%.

Quick developing leukemia's in white blood cells created in the spleen and lymph nodes, called Acute Lymphoblastic Leukemia (ALL), occur most frequently in young children ages 3 to 5 years old. The curability rate for this type of Leukemia in children 3 to 5 is 90%.

Chronic, or slower developing, Leukemia's that occur in white blood cells created in bone marrow most commonly occur in adults. The 5-year overall survival rate for Chronic Granulocytic (Myeloid) Leukemia (CML) is currently about 65%. However in this type of Leukemia, there are different stages of diagnoses. If diagnosed in an early phase, the 5-year survival rate raises to about 85%, but with current treatments and data, patients may have a nearly normal life expectancy.

Slower developing Leukemia that forms in white blood cells created in the spleen and lymph nodes primarily occur in adults in their 60's and 70's. This type of Leukemia, known as, chronic lymphocytic leukemia (CLL), differs in comparison to the other types discussed. It usually does not require treatment immediately, is often diagnosed when blood screenings are performed, like at Delta County's Hospital Health Fairs, and consequently, it is difficult to accurately define a life expectancy.

There is still room for improvement in the treatment of many types of Leukemia's. However, the advances in the treatments options over the last few years, give the patients a great reason to be optimistic for the future.