According to the American Cancer Society, some 43,000 people in the United States are diagnosed with leukemia each year. This includes about:
- 15,000 cases of chronic lymphocytic leukemia (CLL), most in older adults
- 13,500 cases of acute myeloid leukemia (AML), most in adults
- 6,000 cases of acute lymphocytic leukemia (ALL), about one in three in adults
- 5,000 cases of chronic myeloid leukemia (CML), most in older adults
Leukemia is cancer of blood-forming tissue such as the bone marrow, the sponge-like material inside some bones. In healthy bone marrow, blood cells form and mature, then move into the bloodstream. To understand what happens to your blood when you have leukemia, it helps to know what makes up normal blood and bone marrow.
Red Blood Cells (RBCs), the major part of your blood, carry oxygen and carbon dioxide throughout your body. The percentage of RBCs in the blood is called hematocrit. The part of the RBC that carries oxygen is a protein called hemoglobin. All body tissues need oxygen to work properly. When the bone marrow is working normally, the RBC count remains stable. Anemia occurs when there are too few RBCs in the body. Leukemia, or the chemotherapy used to treat it, can cause anemia. Symptoms of anemia include shortness of breath, headache, weakness and fatigue.
White Blood Cells (WBCs) include several different types. Each has its own role in protecting the body from germs. The three major types are neutrophils, monocytes and lymphocytes:
- Neutrophils (also known as granulocytes or polys) destroy most bacteria.
- Monocytes destroy germs such as tuberculosis.
- Lymphocytes are responsible for destroying viruses and for overall management of the immune system. When lymphocytes see foreign material, they increase the body’s resistance to infection.
WBCs play a major role in fighting infection. Infections are more likely to occur when there are too few normal WBCs in the body.
Absolute Neutrophil Count (ANC) is a measure of the number of WBCs you have to fight infections. You can figure out your ANC by multiplying the total number of WBCs by the percentage of neutrophils (“neuts”). The K in the report means thousands. For example:
WBC = 1000 = 1.0K
Neuts = 50% (0.5)
1000 X 0.5 = 500 neutrophils
While anyone can catch a cold or other infections, this is more likely to occur if your ANC falls below 500. Your WBC count generally will fall within the first week you start chemotherapy, but it should be back to normal between 21 and 28 days after starting chemotherapy.
Platelets are the cells that help control bleeding. When you cut yourself, the platelets collect at the site of the injury and form a plug to stop the bleeding.
Bone marrow is the soft tissue within the bones where blood cells are made. All blood cells begin in the bone marrow as stem cells.
The bone marrow is made up of blood cells at different stages of maturity. As each cell fully matures, it is released from the bone marrow to circulate in the bloodstream. The blood circulating outside of the bone marrow in the heart, veins and arteries is called peripheral blood.
Stem cells are very immature cells. When there is a need, the stem cells are signaled to develop into mature RBCs, WBCs or platelets. This signaling is done with “growth factors.”
In leukemia, the normal production of blood cells changes. The bone marrow starts making too many abnormal, immature cells, called blasts or lymphoblasts, which crowd out other blood cells in the blood marrow, blood stream and lymph system. They can travel to other places in the body, including lymph glands and the spleen.
Types of leukemia are grouped by the type of cell affected and by the rate of cell growth. Leukemia can be either acute or chronic.
Acute leukemia involves an overgrowth of very immature blood cells. This condition is life threatening because there are not enough mature blood cells to prevent anemia, infection and bleeding. A diagnosis of acute leukemia is made when there are 20% or more blasts or immature cells in the bone marrow.
There are two main types of acute leukemia:
Acute lymphocyte leukemia (ALL) is most prevalent during childhood and early adulthood, but it also is found in adults.
Acute myeloid (or myelogenous) leukemia (AML) occurs more often in adults.
Myelodysplastic Syndrome (MDS) is a condition in which the bone marrow does not produce enough normal blood cells. Some cases of MDS may, over time, progress to acute leukemia.
Myeloproliferative Disease (MPD), also known as myeloproliferative neoplasia (MPN), is a condition in which the bone marrow makes too many blood cells. Sometimes the disease progresses slowly and requires little treatment; other times it develops into acute myeloid leukemia (AML).
Chronic leukemia involves an overgrowth of mature blood cells. Usually, people with chronic leukemia have enough mature blood cells to prevent serious bleeding and infection. Chronic leukemia is found more often in people between ages 40 and 70. The main types of chronic leukemia are:
- Chronic lymphoblastic leukemia (CLL)
- Chronic myeloid (or myelogenous) leukemia (CML)
To look for specific types of leukemia, your doctor will examine features on the bone marrow cell surface and the appearance of the bone marrow cells under a microscope, as well as analyze chromosome number and appearance.