Chemotherapy (chemo) is treatment with anti-cancer drugs. Chemotherapy can be given in different ways.

Systemic chemotherapy

Systemic chemotherapy uses drugs that are injected into a vein or given by mouth. These drugs enter the bloodstream and reach all areas of the body. This treatment is useful for cancers that have metastasized (spread) beyond the organ they started in.

Regional chemotherapy

In regional chemotherapy, drugs are injected directly into an artery leading to a part of the body containing a tumor. This approach concentrates the dose of chemotherapy reaching the cancer cells. It reduces side effects by limiting the amount reaching the rest of the body.

Hepatic artery infusion: Hepatic artery infusion, where chemotherapy is given directly into the hepatic artery, is an example of regional chemotherapy sometimes used for colon cancer that has spread to the liver.

When is chemotherapy used?

Chemotherapy may be used at different times during the treatment of colon or rectal cancers.

Adjuvant chemotherapy: Chemotherapy used after surgery, known as adjuvant chemotherapy, can increase the survival rate for patients with some stages of colon cancer and rectal cancer. It is given when there is no evidence of cancer remaining but there is a chance that it might come back. The theory behind adjuvant therapy is that a small number of cancer cells may not have been removed by surgery or may have escaped from the primary tumor and settled in other parts of the body. The hope is that the chemotherapy can kill these cells, wherever they may be.

Neoadjuvant chemotherapy: For some rectal cancers, chemotherapy is given (along with radiation) before surgery to try to shrink the cancer and make surgery easier. This is known as neoadjuvant treatment.

Chemotherapy for advanced cancers: Chemotherapy can also be used to help shrink tumors and relieve symptoms for more advanced cancers. While it is very unlikely to be curative in such situations, it may greatly extend survival time in some people.

Drugs used to treat colorectal cancer

Several drugs can be used to treat colorectal cancer. Often, 2 or more of these drugs are combined to try to make them more effective.

5-Fluorouracil (5-FU): This drug had been around for several decades, and it is part of most chemotherapy regimens for colorectal cancer. It is often given together with another drug called leucovorin (or folinic acid), which makes it work better.

This drug may be given as an infusion into a vein over 2 hours, or (more commonly) as a quick injection followed by continuous infusion over 1 or 2 days. For continuous infusions, the patient wears a small battery-operated pump that infuses 5-FU into an intravenous (IV) catheter.

For most chemotherapy regimens, treatment with 5-FU is repeated every 2 weeks, over a period of 6 months to a year.

The possible side effects of this drug include nausea, loss of appetite, mouth sores, diarrhea, low blood cell counts, sensitivity to sunlight, and hand-foot syndrome (pain, sensitivity, and redness in the hands and feet, sometimes along with blistering or skin peeling).

Capecitabine (Xeloda): This is a chemotherapy drug in pill form. Once in the body, it is changed to 5-FU when it gets to the tumor site. This drug seems to be about as effective as giving continuous intravenous 5-FU.

Capecitabine is usually taken twice a day for 2 weeks, followed by a week off.

While this drug may be taken at home as a pill, it is still a strong chemotherapy medicine. The possible side effects are similar to those listed for 5-FU. Although most of the side effects seem to be less common with this drug than with 5-FU, problems with the hands and feet are more common.

Irinotecan (Camptosar): This drug is often combined with 5-FU and leucovorin (known as the FOLFIRI regimen) as a first-line treatment for advanced colorectal cancer. In some cases it may be tried by itself as a second-line treatment if other chemotherapy drugs are no longer effective. It is given as an IV infusion over 30 minutes to 2 hours.

One problem with irinotecan is that some people's bodies aren't able to break down the drug, so it stays in the body and causes severe side effects. This is due to an inherited gene variation that can be tested for. The simplest test is to measure the blood level of bilirubin, a substance made in the liver. If it is slightly elevated, this can be a sign of the gene variation that makes people sensitive to irinotecan. So far, most doctors aren't routinely testing for the gene variant itself.

The major possible side effects of irinotecan are severe diarrhea and low blood counts, although other effects such as nausea are possible as well. Your doctor will likely give you medicine to take before treatment to help prevent diarrhea. You need to tell your doctor right away if you develop diarrhea or any other side effects. Your doctor may not use irinotecan if you are elderly or have serious health problems. In rare cases, severe side effects can even be fatal.

Oxaliplatin (Eloxatin): This drug is usually combined with 5-FU and leucovorin (known as the FOLFOX regimen) or with capecitabine (known as the CapeOX regimen) as a first- or second-line treatment for advanced colorectal cancer. It may also be used as adjuvant therapy after surgery for earlier stage cancers. Oxaliplatin is given as an IV infusion over 2 hours, usually once every 2 or 3 weeks.

Oxaliplatin can affect peripheral nerves, which can cause numbness, tingling, and intense sensitivity to temperature, especially the hands and feet. This goes away in most patients after treatment has stopped, but in some cases it can cause long-lasting nerve damage. If you will be getting oxaliplatin, talk with your doctor about side effects beforehand, and let him or her know right away if you develop numbness and tingling or other side effects.

Side effects of chemotherapy

Chemotherapy drugs work by attacking cells that are dividing quickly, which is why they work against cancer cells. But other cells in the body, such as those in the bone marrow, the lining of the mouth and intestines, and the hair follicles, also divide quickly. These cells are also likely to be affected by chemotherapy, which can lead to side effects.

The side effects of chemotherapy depend on the type and dose of drugs given and the length of time they are taken. General side effects of chemotherapy drugs can include:

• hair loss
• mouth sores
• loss of appetite
• nausea and vomiting
• increased chance of infections (due to low white blood cell counts)
• easy bruising or bleeding (due to low blood platelet counts)
• fatigue (due to low red blood cell counts)

Along with these, some side effects are specific to certain medicines. These are discussed in the descriptions of the individual drugs.

Most side effects are short-term and tend to go away after treatment is finished. There are often ways to lessen these side effects. For example, drugs can be given to help prevent or reduce nausea and vomiting. Do not hesitate to discuss any questions about side effects with the cancer care team.

You should report any side effects or changes you notice while getting chemotherapy to your medical team so that they can be treated promptly. In some cases, the doses of the chemotherapy drugs may need to be reduced or treatment may need to be delayed or stopped to prevent the effects from getting worse.

Elderly people seem to be able to tolerate chemotherapy for colorectal cancer fairly well. There is no reason to withhold treatment in otherwise healthy people simply because of age.

For more general information about chemotherapy, please see the separate American Cancer Society document, Understanding Chemotherapy: A Guide for Patients and Families.

Last Medical Review: 05/18/2009
Last Revised: 05/18/2009