Colon cancer begins in the colon, also known as large intestine. The colon absorbs water and nutrients from foods. Then it passes solid waste to the rectum.
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Cancer is when cells in the body split without control or order. These cells go on to form a growth or tumor. These growths attack nearby tissues. They can also spread to other parts of the body. It’s not clear exactly what causes cancer to develop. It’s likely a mix of genes and the environment.
The risk of colon cancer is higher in those with:
- Age 50 years and older
- Inherited diseases such as familial adenomatous polyposis
- Prior colon or rectal cancer, or polyps
- Certain genes
- Colon or rectal cancer in your family—mainly with a parent, sibling, or child
- Ulcerative colitis or Crohn disease
- Lifestyle factors such as:
Early colon cancer may not cause symptoms. As it grows, colon cancer may cause:
- Bleeding without other problems
- A change in bowel habits
- Blood in the stool that is either bright red, or black and tarry
- Pain or pressure
- Feeling of a mass
- Belly pain
- Weight loss
- Feeling tired
- Breathing problems and pale skin—signs of anemia
Colon cancer screening is recommended for adults 50 years or older. Some with risk factors such as family history or related health issues may start earlier. People who are Black, Asian, or Alaskan Native also have a higher risk of colon cancer. Screening tests that can catch early colon cancer or symptoms include:
- Colonoscopy—every 10 years
- Sigmoidoscopy—every 5 to 10 years
- CT colonography—every 5 years
- Barium enema—every 5 years
- Stool DNA test every 3 years
- Fecal occult blood test (FOBT)—every year
- Fecal immunochemical test (FIT)—every year
More tests or exams will be needed if a screening test suggests cancer. The doctor may also ask for tests if a patient complains about specific symptoms. Tests may include:
- A digital rectal exam—the doctor will feel for lumps with a lubricated, gloved finger in the rectum
- Blood tests
- Colonoscopy or sigmoidoscopy—scope and camera that passes into colon
- Tests to make images of colon and cancer:
- Biopsy —a sample of colon is removed and sent to lab
The exam and test results will confirm cancer and show the stage of cancer. Staging guides treatment. Colon cancer is staged from 0 to 4. Stage 0 is cancer that is still in one area. Stage 4 is a spread to other parts of the body.
Treatment will depend on the stage of cancer and where it is found. It often includes a combination of treatments. Steps may include:
Surgery to remove as much of the cancer as possible. This is the main way to treat colon cancer. Types of surgery include:
- Polypectomy and local excision—Cancer is removed during a sigmoidoscopy or colonoscopy. Used for smaller areas.
- Partial colectomy —The cancer and healthy colon around it are removed. The healthy ends of the colon are reconnected.
- Laparoscopic-assisted colectomy —The cancer and healthy colon around it are removed. It is done through small cuts in the belly.
- Total colectomy—The colon is taken out. A new path for solid waste is also created. Waste will be able to pass through the belly wall to a bag outside the body.
Radiation therapy is the use of radiation to kill cancer cells and shrink tumors. It may be given at the same time as chemotherapy. The types are:
- External—radiation is aimed at the tumor from a source outside the body
- Internal—radioactive materials are placed into the body near the cancer cells
It may be used as part of treatment to get rid of cancer or shrink tumors that are causing problems.
Chemotherapy is the use of drugs to kill cancer cells. It may given by mouth, shots, or IV. The drugs enter the bloodstream and travel throughout the body. It may be used to treat cancer that has spread.
These medicines block tumors from growing and spreading. It may be used with other methods. In many cases, these medicines aren’t used until cancer is in later stages.
Some changes in daily habits may decrease the risk of colon cancer:
- Quit smoking—your doctor will help you find the best way.
- Eat a well-balanced, healthful diet.
- Get at least 30 minutes of activity a day on most days of the week.
- Alcohol—Don’t drink more than 2 a day if you’re a man or more than 1 a day if you’re a woman.
- Keep a healthy weight.
Screening tests can also help to find polyps. Some polyps have an increased risk of becoming cancer if they are not removed. Screening can help to find and remove them before they become a problem.
American Cancer Society
United Ostomy Associations of America
Canadian Cancer Society
Ostomy Canada Society
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Last reviewed January 2021 by EBSCO Medical Review Board Mohei Abouzied, MD, FACP Last Updated: 1/29/2021