Chemotherapy is the use of drugs to destroy cancer cells. It usually works by keeping the cancer cells from growing, dividing, and making more cells. Because cancer cells usually grow and divide faster than normal cells, chemotherapy has more of an effect on cancer cells. However, the drugs used for chemotherapy are powerful, and they can still cause damage to healthy cells. This damage causes the side effects that are linked with chemotherapy.
Different types of chemotherapy
Treatment with these powerful drugs is called standard chemotherapy, traditional chemotherapy, or cytotoxic chemotherapy.
How does chemotherapy treat cancer?
Doctors use chemotherapy in different ways at different times. These include:
Before surgery or radiation therapy to shrink tumors. This is called neoadjuvant chemotherapy.
After surgery or radiation therapy to destroy any remaining cancer cells. This is called adjuvant chemotherapy.
As the only treatment. For example, to treat cancers of the blood or lymphatic system, such as leukemia and lymphoma.
For cancer that comes back after treatment, called recurrent cancer.
For cancer that has spread to other parts of the body, called metastatic cancer.
The goals of chemotherapy
The goals of chemotherapy depend on the type of cancer and how far it has spread. Sometimes, the goal of treatment is to get rid of all the cancer and keep it from coming back. If this is not possible, you might receive chemotherapy to delay or slow cancer growth.
Delaying or slowing cancer growth with chemotherapy also helps manage symptoms caused by the cancer. Chemotherapy given with the goal of delaying cancer growth is sometimes called palliative chemotherapy.
Your chemotherapy plan
There are many drugs available to treat cancer. A doctor who specializes in treating cancer with medication, called a medical oncologist, will prescribe your chemotherapy. You may receive a combination of drugs, because this sometimes works better than only 1 drug.
The drugs, dose, and treatment schedule depend on many factors. These include:
The type of cancer
The tumor size, its location, and if or where it has spread. This is called the stage of cancer.
Your age and general health
Your body weight
How well you can cope with certain side effects
Any other medical conditions you have
Previous cancer treatments
Where is chemotherapy given?
Your health care team may give you chemotherapy at the clinic, doctor's office, or hospital. Some types of chemotherapy are given by mouth, and these can be taken at home.
How long does chemotherapy take?
Chemotherapy is often given for a specific time, such as 6 months or a year. Or you might receive chemotherapy for as long as it works.
Side effects from many drugs are too severe to give treatment every day. Doctors usually give these drugs with breaks, so you have time to rest and recover before the next treatment. This lets your healthy cells heal.
For example, you might get a dose of chemotherapy on the first day and then have 3 weeks of recovery time before repeating the treatment. Each 3-week period is called a treatment cycle. Several cycles make up a course of chemotherapy. A course usually lasts 3 months or more.
Some cancers are treated with less recovery time between cycles. This is called a dose-dense schedule. It can make chemotherapy more effective against some cancers. But it also increases the risk of side effects. Talk with your health care team about the best schedule for you.
How is chemotherapy given?
Chemotherapy may be given in several different ways, which are discussed below.
Intravenous (IV) chemotherapy. Many drugs require injection directly into a vein. This is called intravenous or IV chemotherapy. Treatment takes a few minutes to a few hours. Some IV drugs work better if you get them over a few days or weeks. You take them through a small pump you wear or carry. This is called continuous infusion chemotherapy.
Oral chemotherapy. You can take some drugs by mouth. They can be in a pill, capsule, or liquid. This means that you may be able to pick up your medication at the pharmacy and take it at home. Oral treatments for cancer are now more common. Some of these drugs are given daily, and others are given less often. For example, a drug may be given daily for 4 weeks followed by a 2-week break.
Injected chemotherapy. This is when you receive chemotherapy as a shot. The shot may be given in a muscle or injected under the skin. You may receive these shots in the arm, leg, or abdomen. Abdomen is the medical word for your belly.
Chemotherapy into an artery. An artery is a blood vessel that carries blood from your heart to another part of your body. Sometimes chemotherapy is injected into an artery that goes directly to the cancer. This is called intra-arterial or IA chemotherapy.
Chemotherapy into the peritoneum or abdomen. For some cancers, medication might be placed directly in your abdomen. This type of treatment works for cancers involving the peritoneum. The peritoneum covers the surface of the inside of the abdomen and surrounds the intestines, liver, and stomach. Ovarian cancer is one type of cancer that frequently spreads to the peritoneum.
Topical chemotherapy. You can take some types of chemotherapy in a cream you put on your skin. You get your medication at the pharmacy and take it at home.
Other drug treatments for cancer
The traditional drugs used for chemotherapy are an important part of treatment for many cancers. The drugs affect both cancer cells and healthy cells. But scientists have designed newer drugs that work more specifically to treat cancer. These treatments cause different side effects.
Doctors may use these newer cancer drugs as the only drug treatment. But they are often added to traditional chemotherapy. These types of treatment include:
Hormonal therapy. These treatments change the amount of hormones in your body. Hormones are chemicals your body makes naturally. They help control the activity of certain cells or organs. Doctors use hormonal therapy because hormone levels control several types of cancers. These include some breast and prostate cancers.
Targeted therapy. These treatments target and disable genes or proteins found in cancer cells that the cancer cells need to grow.
Immunotherapy. This type of treatment helps your body's natural defenses fight the cancer. Immunotherapy is now an important part of treatment for several types of cancer and will play an increasingly important role in treatment in the future.