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Chemotherapy (chemo) is the use of cancer-killing drugs. These drugs can be put into a vein, given as a shot, or taken as a pill or liquid. They enter the bloodstream and reach most parts of the body, making this treatment useful for cancers that have spread to distant organs. While these drugs kill cancer cells, they also damage some normal cells, which can lead to side effects.

When is chemo used?

Chemo can be used either before or after surgery for early-stage breast cancer. This is to kill any cancer cells that may have spread but are too small to be seen by exam or tests. When chemo is given after surgery to patients who have no signs of cancer spread it is called adjuvant chemo. This lowers the chance of the cancer coming back later. When chemo is given before surgery to cure the cancer it is called neoadjuvant chemo. This can shrink large cancers so that they are small enough to be removed with breast-conserving surgery instead of mastectomy. It also works as well as adjuvant chemo in lowering the chance that the cancer will come back later.

Chemo can also be used as the main treatment for women with cancer that has spread to distant sites (outside the breast and the nearby lymph nodes).

How is chemo given?

Doctors give chemo in cycles, with each round of treatment followed by a rest period. The time between cycles (the beginning of each treatment) is most often 2 or 3 weeks, but can vary according to the drug or combination of drugs being used. For early-stage breast cancer, the total course of treatment usually lasts for 3 to 6 months. For advanced breast cancer chemo is often continued as long as it is working.

Menstrual periods often stop for a time while you are on chemo. But this doesn’t mean that you can’t get pregnant. Getting pregnant while having chemo could lead to birth defects and cause problems with treatment. If you are having sex, you should discuss birth control with your cancer doctor.

Possible side effects

The side effects of chemo depend on the type of drugs used, the amount given, and the length of treatment. You could experience some of these short-term side effects:

  • Hair loss
  • Loss of appetite or increased appetite
  • Nausea and vomiting
  • A higher risk of infection (from low white blood cell counts)
  • Stopping of menstrual periods
  • Easy bruising or bleeding (from low blood platelet counts)
  • Being very tired (called fatigue, often caused by low red blood cell counts or other reasons)

Most of these side effects go away when treatment is over. For example, your hair will grow back and your blood counts will return to normal. If you have any problems with side effects, be sure to tell your doctor or nurse because there are often ways to help.

Possible long-term side effects

Menstrual changes: Many women find their menstrual periods stop on chemo. For some, they don’t start again and the women go through the change of life (menopause). Some women may have their periods start again, but find that they can’t become pregnant (they are infertile). Still, having your periods stop doesn’t mean you can’t get pregnant.

Nerve damage: Some drugs used to treat breast cancer can damage nerves. This can sometimes lead to symptoms (mainly in the hands and feet) such as pain, burning or tingling, sensitivity to cold or heat, or weakness. In most cases this goes away once treatment is stopped, but for some women it may last a long time. You can learn more about this in Peripheral Neuropathy Caused by Chemotherapy

Heart damage: Some of the drugs may cause heart damage if used for a long time or in high doses. Doctors check a patient’s heart function before giving these drugs. They also are careful to control the doses of these drugs and watch for signs of problems.

For more information about the chemo used to treat breast cancer, see the Breast Cancer detailed guide.

Last Medical Review: 09/09/2014
Last Revised: 01/14/2016