Colorectal Cancer

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What is colorectal cancer?

Colon cancer is cancer of the large intestine (called the colon). Rectal cancer is cancer of the rectum (which is the part of the large intestine closest to the anus). These forms of cancer have many common features. They are often referred to together as colorectal cancer.

Colorectal cancer is the second leading cause of cancer deaths in the United States. Many of these deaths happen when the cancers are found too late to be effectively treated. If colorectal cancer is found early enough, it is usually very treatable and not life threatening.


What are the signs and symptoms of colorectal cancer?

Most colorectal cancers begin as a polyp (say: “pohl-ip”). At first, a polyp is a small, harmless growth in the wall of the colon. However, as a polyp gets larger, it can develop into a cancer that grows and spreads.

See your doctor if you have any of the following warning signs:

  • Bleeding from your rectum
  • Blood in your stool or in the toilet after you have a bowel movement
  • A change in the shape or consistency of your stool (such as diarrhea or constipation lasting several weeks)
  • Cramping pain in your lower stomach
  • A feeling of discomfort or an urge to have a bowel movement when there is no need to have one
  • Weakness or fatigue
  • Unintended weight loss

Other conditions can cause these same symptoms. You should see your doctor to find what is causing your symptoms.

Causes & Risk Factors

When should I be screened for colorectal cancer?

Colorectal cancer is more common in older people, so doctors usually screen people 50 years of age and older. Some people have risk factors that make them more likely to get colorectal cancer at a young age. Screening should begin earlier in these people.

You should be screened for colorectal cancer at a younger age if:

  • You have had colorectal cancer or polyps in the past
  • You have a family history of colorectal cancer or polyps
  • You have ulcerative colitis or Crohn’s disease
  • You have a hereditary colon cancer syndrome

If you are in one of these groups, you may also need to be tested more often than a person who doesn’t have risk factors for colorectal cancer.

Any one of the screening programs (with a digital rectal exam at each screening) may be used every 5 to 10 years, beginning at 50 years of age.

Talk to your family doctor to decide which screening tests you should have and how often you should be screened. If you don’t have any risk factors for colorectal cancer, you will probably have your first screening test around 50 years of age.

Diagnosis & Tests

What are screening tests for colorectal cancer?

Screening tests can find polyps or cancers before they are large enough to cause any symptoms. Screening tests are important because early detection means that the cancer can be more effectively treated. Your doctor will choose the tests that are right for you. The following are some screening tests for colorectal cancer:

Digital Rectal Exam. In this exam, your doctor puts his or her gloved finger into your rectum to find any growths. This exam is simple to do and is not painful. However, because this exam can find less than 10% of colorectal cancers, it must be used along with another screening test.

Barium Enema. For this test, you are given an enema (injection of fluid into the rectum) with a liquid that makes your colon show up on an X-ray. Your doctor looks at the X-ray to find abnormal spots in your entire colon. If you have an abnormal spot or if the radiologist detects polyps in your colon, your doctor will probably want you to have colonoscopy.

Fecal Occult Blood Test. This test checks your stool for blood that you can’t see. Your doctor gives you a test kit and instructions to use it at home. Then you return a stool sample to your doctor for testing. If blood is found, another test is done to look for a polyp, cancer or another cause of bleeding. Your doctor will also ask you to not eat certain foods or take certain medicines that may interfere with test results a few days before the test.

Certain foods and medicines can make this test turn out positive, even though you don’t really have blood in your stool. This is called a “false-positive” test. These include some raw vegetables, horseradish, red meat, non-steroidal anti-inflammatory drugs (such as ibuprofen), blood thinners, vitamin C supplements, iron supplements and aspirin. Some medical conditions, like hemorrhoids, can also cause a false-positive test result.

Stool DNA Test. This test checks your stool for cells that are shed by colon cancers or precancerous polyps. Your doctor will give you a test kit with instructions on how to collect a stool sample. Your doctor may also ask you to not eat certain foods or take certain medicines that may interfere with test results a few days before the test. If your test turns out positive, your doctor will probably want you to have a screening test called colonoscopy.

Colonoscopy. Before you have this test, you are given a medicine to make you relaxed and sleepy. A thin, flexible tube connected to a video camera is put into your rectum, which allows your doctor to look at your entire colon. The tube can also be used to remove polyps and cancers during the exam. Colonoscopy may be uncomfortable, but it is usually not painful.

Virtual Colonoscopy. This is a new test that uses a computerized tomography (CT) machine to take pictures of your colon. Your doctor can then see all of the images combined in a computer to check for polyps or cancer. If your doctor finds polyps or other abnormalities in your colon, you will need to have a traditional colonoscopy to examine them in more detail or to remove them.

Flexible Sigmoidoscopy. In this test, your doctor puts a thin, flexible, hollow tube with a light on the end into your rectum. The tube is connected to a tiny video camera so the doctor can look at the rectum and the lower part of your colon.

This test can be a bit uncomfortable, but it lets your doctor see polyps when they are very small (before they can be found with a fecal occult blood test). Because flexible sigmoidoscopy may miss cancerous polyps that are in the upper part of the colon, some doctors prefer a colonoscopy. Your doctor will discuss these options with you.


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.

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Questions to Ask Your Doctor

  • How often should I be screened for colorectal cancer?
  • I’ve seen information about fecal occult blood tests I can do at home. Are they a good way to screen for colorectal cancer?
  • Am I at risk for colorectal cancer?
  • Do treatments for colorectal cancer cure the disease?
  • How long will my treatment last?
  • After my treatment is over, how often should I be screened for colorectal cancer?
  • I’ve had constipation or diarrhea for several weeks. Could this be colorectal cancer?
  • Is there one screening test for colorectal cancer that works the best?
  • Is colorectal cancer something that runs in families?