Chemotherapy—The use of drugs to destroy cancer cells. A person on chemotherapy may take one drug or a combination of drugs. Most often these drugs are given by vein using intravenous (IV) infusion. Some can be taken by mouth or given in a shot.

Chemotherapy Regimen—A plan of drug treatment, including doses, scheduling, and duration of administration.

Colony-stimulating factors— Also called CSFs, colony-stimulating factors are drugs that promote the production of various blood cells. Example of CSFs is Neulasta^® (pegfilgrastim).

Complete blood count (CBC)—The CBC is a test that determines the number of red blood cells, white blood cells, and platelets in the blood.

Infection—An invasion of microorganisms that have the ability to multiply and produce disease.

Neutropenia—Neutropenia occurs if there is a lower-than-normal number of neutrophils (infection-fighting white blood cells) in the blood. It is a common side effect of chemotherapy treatment. Doctors check the number of neutrophils when they measure the white blood cell count, to monitor the risk of infection.

Neutrophil—The most common type of white blood cell. Neutrophils help the body fight infection. A low white blood cell count usually indicates that the neutrophil count is low. It is easier to get an infection and harder to recover from an infection when the number of neutrophils in the bloodstream is low.

Oncologist—A doctor who specializes in the treatment of cancer.

Oncology—The branch of medicine that focuses on the study and treatment of cancer.

Red blood cell—Red blood cells are made in the bone marrow and released into the blood. They circulate in the blood and carry oxygen and carbon dioxide to and from every cell in the body.

Risk factor—Anything that increases the chance of getting a certain disease, such as cancer. Some risk factors are genetic while others are environmental.

Side effect—Any undesired actions or effects of a drug or treatment. For example, common side effects of chemotherapy include fatigue, nausea, vomiting, and loss of appetite.

White blood cell (WBC)—A white blood cell is one of the three main types of blood cells. White blood cells are responsible for fighting infection. There are several kinds of white blood cells, including monocytes, lymphocytes, neutrophils, eosinophils, and basophils.