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The goal of cancer treatments like chemotherapy and radiation therapy is to destroy cancerous cells in the body. However, some of the body’s normal cells are sensitive to these treatments and may also be damaged in the process. In addition, some cancer treatments can interfere with the body’s production of blood cells. For instance, chemotherapy can cause white blood cells to be destroyed faster than the bone marrow can make new ones.
Types of Blood Cells
There are three basic types of blood cells, each with different functions in the body. White blood cells (WBCs), also called leukocytes, fight infections in the body. Red blood cells (RBCs), also called erythrocytes, carry oxygen from the lungs to cells throughout the body. Platelets, also called thrombocytes, are involved in blood clotting.
Nadir: A Drop in Blood Cell Counts
Nadir is a term used to describe the point after cancer treatment when blood counts are at their lowest. The nadir for each blood cell type will occur at different times. For instance, WBCs will usually reach their nadir within seven to 14 days following the last day of chemotherapy treatment. A person is most vulnerable to infection at this point. Within three or four weeks, the blood counts will slowly rise again to a normal level.
During cancer treatment, your doctor will do routine blood tests, such as a complete blood count (CBC), to check the levels of WBCs, RBCs, and platelets in your blood. Sometimes, a sample of bone marrow may be taken as well.
Low White Blood Cell Counts (Neutropenia)
White blood cells help protect the body by fighting bacteria, viruses, and other foreign invaders that cause infections. One type of WBC, neutrophils, make up the majority of WBCs and are the body’s main defense against infections. Neutropenia results from an abnormally low level of neutrophils in the blood.
When your neutrophil count is low, your doctor may delay further treatment or recommend a lower dose until your WBC count returns to a normal level. Your doctor may also prescribe antibiotics as a preventive measure and recommend a variety of precautions, such as hand washing.
There are also certain drugs or other therapies that may be used to treat neutropenia. For example, growth factors (also known as granulocyte-colony stimulating factors, or G-CSFs) may be used to stimulate the bone marrow to produce neutrophils. Some growth factors include Neupogen®, Neulasta®, and Leukine®.
|WBC||4.5 - 11.0||1.5 or below|
Low Red Blood Cell Counts (Anemia)
Red blood cells contain a substance called hemoglobin, which carries oxygen throughout the body. Hemoglobin and hematocrit are the tests used to evaluate RBCs. Anemia results from a low RBC count. Anemia is a common problem for people fighting cancer, particularly blood cancers like lymphoma or leukemia. Fewer red blood cells mean your body is getting less oxygen for energy and function.
When your RBC count is low, the body tissues are not getting enough oxygen to function properly and you may experience fatigue. If your RBC counts become dangerously low, you may require a transfusion (intravenous delivery of blood) to raise RBC levels and help restore energy.
Also, certain medications can stimulate RBC production, such as erythropoietin. These growth factors (e.g., Aranesp®, Procrit®, Epogen®) are generally given by subcutaneous injection (a shot under the skin). If poor diet is the cause of anemia, eating a balanced diet and taking iron and folic acid supplements may help.
|Hemoglobin||12.0 - 16||8.0 or below|
|Hematocrit||38 - 47||None|
Low Platelet Counts (Thrombocytopenia)
Platelets help your blood to clot and prevent excessive bleeding. Decreased levels of platelets during cancer treatment can cause bleeding or bruising. Thrombocytopenia is a low blood platelet count.
Fortunately, platelet levels usually return to normal following the completion of chemotherapy. If your platelet count is extremely low, you may be given a blood or platelet transfusion to restore the count to normal.
|Platelet Count||150 - 450||30 or below|