Chemotherapy is the use of chemical substances to treat disease. In its modern-day use, it refers primarily to cytotoxic drugs used to treat cancer.

Depending on the type of cancer and how advanced it is, chemotherapy can be used for different goals:

To cure the cancer. Cancer is considered cured when the patient remains free of evidence of cancer cells.

To control the cancer. This is done by keeping the cancer from spreading; slowing the cancer's growth; and killing cancer cells that may have spread to other parts of the body from the original tumor.

To relieve symptoms that the cancer may cause. Relieving symptoms such as pain can help patients live more comfortably.

Ideal candidates for chemotherapy are patients who have been diagnosed with cancer.

Some chemotherapy drugs are used for many different types of cancer, while others might be used for just one or two types of cancer. Your doctor recommends a treatment plan based on:

• What kind of cancer you have.
• What part of the body the cancer is found.
• The effect of cancer on your normal body functions.
• Your general health.

A doctor called an oncologist will make the decision about which type of chemo is best for the patient. A person might take a pill or liquid or get an injection (shot). Another way of giving chemo is through an IV line, which is short for an intravenous line.

An IV line is a tiny tube that's put into a vein through someone's skin, usually on the arm. The IV line is attached to a bag or pump that holds the medicine. The chemo medicine flows from the bag or pump into the vein, which puts the medicine into the blood. Once the medicine is in the blood, it can travel through the body and attack cancer cells.

Sometimes doctors will insert a permanent IV line into a larger vein in the upper chest. This type of IV line is also called a catheter. It allows a person to get chemo and other medicines easily without having to get a needle in the arm each time. Although it's called permanent, this type of catheter only stays in place until the person is finished with his or her cancer treatments. In addition to letting a person get chemo without having a new IV line inserted each time, a catheter lets doctors and nurses take blood samples and give other treatments without sticking the person with a needle.

Chemotherapy is carefully planned and is usually given as a series of sessions of treatment. Each session is followed by a rest period. The session of chemotherapy and the rest period is known as a cycle of treatment. A series of cycles makes up a course of treatment. Each session of chemotherapy destroys more of the cancer cells, but the rest period allows the normal cells and tissues to recover.

Side effects from chemotherapy can include pain, diarrhea, constipation, mouth sores, hair loss, nausea and vomiting, as well as blood-related side effects. In this section, you can learn more about the importance in diagnosing and monitoring blood-related side effects. These may include low white blood cell count (neutropenia), low red blood cell count (anemia), low platelet count (thrombocytopenia), and related fatigue.

Chemotherapy works by destroying cancer cells; unfortunately, it cannot tell the difference between a cancer cell and some healthy cells. So chemotherapy eliminates not only the fast-growing cancer cells but also other fast-growing cells in your body, including, hair and blood cells.

The kinds of treatment used to fight cancer depend on the type of cancer and in how many parts of the body the cancer is found. Chemo is given on a schedule. Some people receive chemo every day. Others receive it every week or every month. Doctors use the word cycles to describe chemo because the treatment periods happen between periods of rest when a person isn't getting any treatment. These breaks allows the person's body to heal from the effects the chemo has on the cancer and on the body's normal cells.

Breaks from treatment are important because, during chemo, a person might experience some temporary health problems. These temporary problems are called side effects. All medications can have side effects. In their effort to kill cancer cells, chemo drugs can make normal cells sick. Breaks during chemo cycles allow time for normal cells to get better