Colorectal Cancer | Treatment


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 is treatment with drugs that kill cancer cells. Chemotherapy is often used when there is a risk that the colon or rectal cancer will come back.
  • Radiotherapy, also sometimes called radiation, is treatment with X-rays that kill cancer cells. Radiotherapy 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 of stages for tracking the level of colon or rectal cancer. These stages are referred to as stage I, stage II, stage III and stage IV. The stage describes 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 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 radiation 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, surgery alone has a high cure rate. 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 and possibly into nearby tissue. If the cancer is in your rectum, your doctor may want you to have both radiation therapy and chemotherapy before the surgery to remove the tumor. However, for people who have colon cancer, there is still some debate about whether it is best to give chemotherapy before or after surgery. Talk to your doctor about the pros and cons of this treatment.

Some stage II colon cancers have a high risk of recurrence (coming back). The tumor that is 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 also have chemotherapy for about 6 months after surgery. Radiation may be used to try to kill any remaining cancer cells.

What does stage III cancer mean?

Stage III cancer of the colon or rectum means the cancer has spread to the lymph nodes. The risk that the cancer will come back is high. Recent research studies of patients who have stage III cancer have shown that when chemotherapy, radiation 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 distant metastasis. A stage IV metastatic cancer is almost never curable. Chemotherapy is offered to people who have this stage of colon or rectal cancer to control their symptoms and lengthen survival.

How is chemotherapy used to treat colon and rectal cancer?

Chemotherapy drugs are used to kill cancer cells that may have been left behind after a tumor is 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 may be used to treat colon and rectal cancer. With colorectal cancer, there is a risk that the cancer may come back in the pelvic area. Radiation reduces this risk. If you have stage II or III colorectal 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, radiation therapy is given before surgery for rectal cancer to shrink the tumor and prevent return of the cancer in that area. At other hospitals, radiation is given after surgery only if there is an increased risk of the cancer returning or spreading.

What about side effects?

Cancer treatment affects people 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 should 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 is the best timing or length of treatment. Your doctor can help you decide if you want to participate in a clinical research program.

I have been diagnosed with colon cancer. How often should I have a blood test?

You should probably have a CEA (carcinoembryonic antigen) blood test every 3 months for the first 2 years after your cancer diagnosis. Your doctor will recommend how often after that you should be checked. CEA testing, combined with CT (computed tomographic) scans, can improve survival. Talk to your doctor about how often you should have a CT scan. Most people should have a colonoscopy 1 year after surgery, and again every 3 years.


Update on Colorectal Cancer by DR Rudy, MJ Zdon (American Family Physician March 15, 2000,

Written by editorial staff

Reviewed/Updated: 04/14
Created: 09/00