What is colon cancer?

Colon cancer happens when cells that are not normal grow in your colon. These cells often form in polyps, which are small growths in the colon. Not all colon polyps turn into cancer. But most colon cancer starts in a polyp.

Colon cancer occurs most often in people older than 50.

What happens when you have colon cancer?

Colon cancer usually grows very slowly. It usually takes years for the cancer to become large enough to cause symptoms. If the cancer is not removed and keeps growing, it eventually will invade and destroy nearby tissues and then spread farther, first to nearby lymph nodes. From there it may spread to other parts of the body.

What are the symptoms?

Colon cancer in its early stages usually doesn't cause any symptoms. Symptoms occur later, when the cancer may be harder to treat. The most common symptoms include:

• Blood in your stool or very dark stools.
• A change in your bowel habits, such as more frequent stools or a feeling that your bowels are not emptying completely.
• Pain in the belly or rectal pain.
• Low energy.

How can you prevent colon cancer?

Screening tests can find or prevent many cases of colon cancer. They look for a certain disease or condition before any symptoms appear.

Screening tests that may find colon cancer early include:

• Stool tests, such as the fecal immunochemical test or the guaiac fecal occult blood test.
• Sigmoidoscopy, which lets your doctor look at the inside of the lower part of your colon using a lighted tube.
• Colonoscopy, which lets your doctor look at the inside of your entire colon using a thin, flexible tube.

Your risk for colorectal cancer gets higher as you get older. Experts say that most adults should start regular screening at age 50 and stop at age 74. Talk with your doctor about your risk and when to start and stop screening.

People with a higher risk, such as those with a strong family history of colon cancer, should be tested earlier than those with an average risk.

Here are other things you can do to help prevent colon cancer:

• Watch your weight. Being very overweight may increase your chance of getting colon cancer.
• Eat well. Eat more whole grains, fruits, vegetables, poultry, and fish. And eat less red meat, refined grains, and sweets.
• If you drink alcohol, try to drink less. The more alcohol you drink, the greater your risk for cancer and other health problems. Your risk of harm from alcohol is low if you have 2 drinks or less per week, moderate if you have 3 to 6 drinks per week, and high if you have 7 or more drinks per week.
• Get active. Keep up a physically active lifestyle.
• Quit smoking. If you smoke cigarettes, quit smoking to reduce your chance of getting colon cancer.

How is colon cancer treated?

Treatment for colon cancer is based on the stage and location of the cancer. It's also based on other things, such as your overall health. Most people have surgery to remove the cancer. Chemotherapy, radiation therapy, or both may also be used. In some cases, targeted therapy may be an option.