Chemotherapy and Radiotherapy for Cancer of the Colon or Rectum

How is cancer of the colon or rectum treated?

If you have cancer of the colon or rectum, your doctor will probably talk to you about various treatment options. Surgery to remove the tumor is usually the main treatment for colon and rectal cancer. Chemotherapy (treatment with drugs that kill cancer cells) is often used when there is a risk that the colon or rectal cancer will come back. Radiotherapy (treatment with x-rays that kill cancer cells) may be used either before or after surgery for rectal cancer. Sometimes both radiotherapy and chemotherapy are used after surgery.

What is cancer staging?

Doctors use a system that puts colon or rectal cancer into 1 of 4 stages. These stages are referred to as stage I, stage II, stage III and stage IV. The stage depends on how deep the cancer is in the wall of the colon or rectum and how much the cancer has spread to the lymph nodes (small structures in the body that produce and store cells that fight infection) or other organs.

Stage I cancer is the earliest stage. Stage IV is the most advanced stage. The higher the cancer stage, the more the cancer has spread and the lower your chance for cure. Doctors also use staging to decide whether to use additional treatments (such as radiotherapy or chemotherapy) to prevent the cancer from coming back after surgery.

What does stage I cancer mean?

Stage I cancer of the colon or rectum means that the tumor is only in the inner layer of your colon or rectum and has not spread further through the wall of your colon or rectum. Stage I cancer has a good chance of being cured. For this stage of colon or rectal cancer, the cure rate with surgery alone is high. Chemotherapy and radiotherapy are usually not needed.

What does stage II cancer mean?

Stage II cancer of the colon or rectum means the tumor has grown deeper into the wall than with stage I cancer. Stage II cancer goes through the inner layer of the colon or rectum but usually does not go completely through the wall. There are some stage II colon cancers that have a high risk of recurrence (coming back). The tumor that was removed at surgery will be examined in a lab to help your doctor tell whether the cancer has a high risk of recurrence. If you have a stage II cancer with a high risk of recurrence, your doctor may recommend that you have chemotherapy. Radiotherapy may be used if you have rectal cancer.

What does stage III cancer mean?

Stage III cancer of the colon or rectum means the cancer has spread to the lymph nodes. When colon or rectal cancer has spread to your lymph nodes, the risk that the cancer will come back is high. Recent research studies of patients with stage III cancer have shown that when chemotherapy, radiotherapy or both are used in addition to surgery, survival rates are better and the cancer is less likely to come back.

What does stage IV cancer mean?

Stage IV cancer of the colon or rectum means that the cancer has spread to another part of the body, such as the liver or bone. This spread is called metastasis. A metastatic cancer cannot be cured. Chemotherapy is offered to people with this stage of colon or rectal cancer to control their symptoms.

How is chemotherapy used to treat colon and rectal cancer?

Chemotherapy is used to kill cancer cells that may have been left behind after a tumor was removed by surgery. Chemotherapy is usually combined with another treatment called immunotherapy. During immunotherapy, a person takes drugs that help the immune system fight cancer. Research has shown that the combination of chemotherapy (to kill cancer) and immunotherapy (to help the immune system fight cancer) helps prevent the spread of colon and rectal cancer better than just chemotherapy.

Many different drugs are available for chemotherapy and immunotherapy treatments. Your doctor will help you decide which drugs are right for your treatment needs.

When is radiotherapy used?

Radiotherapy (also called radiation) may be used to treat rectal cancer. With rectal cancer, there is a risk that the cancer may come back in the pelvic area. Radiotherapy reduces this risk. If you have a stage II or III rectal cancer, the risk of the cancer coming back is great enough to justify the use of radiotherapy in addition to surgery. Chemotherapy and radiotherapy together have been shown to improve the outcome in rectal cancer treatment.

At many medical centers, radiotherapy is given before surgery for rectal cancer to shrink the tumor and prevent return of the cancer in that area. At other hospitals, radiotherapy is given after surgery only if there is an increased risk of the cancer returning or spreading. There is still some debate about whether it is best to give radiotherapy to people with rectal cancer before or after surgery.

What about side effects?

Cancer treatment affects every person differently. Some people have few side effects or none at all. However, the side effects of cancer treatment make many people feel very sick.

Your doctor will tell you what kinds of side effects you might expect with your cancer treatment. He or she will also tell you which side effects are unusual and when you need to call the doctor's office.

What are clinical research programs?

While the use of chemotherapy and radiotherapy after surgery for colon and rectal cancers is now standard practice, doctors still want to learn more. These treatments are being studied in an effort to keep improving results. You may be given the opportunity to participate in a clinical research program to help doctors learn which drugs are more effective or what the best timing or length of treatment is. Your doctor can help you decide if you want to participate in a clinical research program.

I was diagnosed with colon cancer a year ago; how often should I have a blood test?

You should have a CEA (carcinoembryonic antigen) blood test every three months for the first two years after your cancer diagnosis, then every six months for about five years after that. CEA testing, combined with CT (computed tomographic) scans, can improve survival. Talk to your doctor about how often you should have a CT scan. You should have a colonoscopy one year after your surgery, and again every three years.


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Written by familydoctor.org editorial staff.

American Academy of Family Physicians

Reviewed/Updated: 08/06
Created: 09/00