What is colon cancer?

Colon cancer is a tumor of the large intestine (colon) that can spread to other parts of the body and cause death. Colon cancer is the second most common cause of cancer-related death in the United States. Most people with colon cancer get better if the cancer is found early.

Rectal cancer is a type of colon cancer that starts at the end of the large intestine (called the rectum). The term “colorectal cancer” is sometimes used for cancer of the colon and rectum.

What are the symptoms of colon cancer?

Colon cancer causes blood in the stool, stomach pain, and a change in bowel movements (for example, a change in the width of your stool). Some people don't have any symptoms. If you don't have symptoms, it is more likely that the tumor will not be found and will continue to grow. Screening tests can find cancer and small tumors (called polyps [PAW-lips]) that can turn into cancer over time.

Who should be screened?

It is recommended that healthy people 50 years and older get screened. You should continue screening until you are 75 years old. If you have symptoms of colon cancer or if you are at risk of colon cancer, your doctor may suggest getting screened before 50 years of age. You are at risk of colon cancer if you have a parent, brother, or sister who has or had colon cancer, polyps, or other less common conditions (for example, inflammatory bowel disease).

What are some colon cancer screening tests?

Fecal occult blood test (“stool cards”). This test is done at home once a year. You take a stool sample from three bowel movements in a row and give it to your doctor for testing. This test decreases death from colon cancer, and costs about $30. But, it has low accuracy and works only if it is done every year. If the test is abnormal, you will still need to have a colonoscopy (ko-len-OS-KO-pee).

Flexible sigmoidoscopy (sig-moyd-OS-KO-pee). This test is done every five years. It can be used with stool cards, but this is not required. For this test, your doctor will insert a thin, lighted tube into your rectum. The tube is connected to a video camera so the doctor can look at your rectum and the lower part of your colon. You will have to take laxatives the day before or the morning of the test to clean out your colon. You will be awake during the test, and you will probably be able to go back to work after the test. This test decreases death from colon cancer and is more accurate than stool cards alone. It is safer and costs less than colonoscopy (about $400), but it is not as accurate. If the test is abnormal, you will still need to have a colonoscopy.

Colonoscopy. This test is done every 10 years. For this test, your doctor will give you medicine to make you sleepy. He or she will then insert a thin tube connected to a video camera into your rectum to look at your whole colon. You will have to take laxatives the day before the test to clean out your colon. If polyps are found during the test, they can usually be removed right away. You will probably miss a day of work and someone will have to drive you home after the test. This test may not be available at smaller hospitals. Colonoscopy is the most accurate test, but it also is the most expensive (about $1,500 to $2,000). It causes more injuries than the other tests (one or two people will be injured for every 1,000 people who have the test). If your colon is injured during the test, you may need surgery to repair it.

CT colonography (ko-len-OG-RA-fee). This test is also called a “virtual” or “x-ray” colonoscopy. It is a newer test, and the best way to use it has not been decided. Also, how much it costs and how safe it is compared with the other tests is not clear. For this test, compressed air is pumped into your rectum through a tube. Then, a picture is taken of your colon. You will have to take laxatives the day before the test to clean out your colon. This test is almost as good at finding large polyps as colonoscopy, but it is less accurate overall, especially for finding small polyps. If the test is abnormal, you will still need to have a colonoscopy.

How can I prevent colon cancer?

The only way to prevent colon cancer is to find polyps early and have them removed. Being obese or not getting enough exercise increases your risk of getting colon cancer. Eating less fat and taking aspirin or ibuprofen (one brand: Motrin) may lower your risk of getting polyps. But, aspirin and ibuprofen may cause gastrointestinal bleeding and renal problems.

Women who have gone through menopause may lower their risk of colon cancer by taking hormones. But, hormones have side effects, including blood clots and a higher risk of breast cancer. Taking fiber or antioxidants (for example, vitamin A) does not decrease the risk of colon cancer.