Colon Cancer



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 is not clear exactly what causes cancer to develop. It is likely a mix of genes and the environment.

Risk Factors

The risk of colon cancer is higher in people over 50 years old and those with:

  • Inherited diseases such as familial adenomatous polyposis
  • Past colon or rectal cancer , or polyps
  • Certain genes
  • Colon or rectal cancer in the family—mainly with a parent, sibling, or child
  • Ulcerative colitis or Crohn disease
  • Obesity
  • Habits such as:
    • Smoking
    • Eating a diet high in red meat, and low in fruits, vegetables, and whole grains
    • Drinking excess alcohol
    • Little or no physical activity



Early colon cancer may not cause symptoms. As it grows, colon cancer may cause:

  • Rectal bleeding without other problems
  • A change in bowel habits, such as looser or more frequent stools (poop)
  • Blood in the stool (poop) that is either bright red, or black and tarry
  • Pain or pressure
  • Feeling of a mass
  • Anal itching or soreness
  • Belly pain
  • General symptoms, such as:
    • Weight loss without trying
    • Feeling tired
    • Breathing problems and pale skin—signs of anemia


Colon cancer screening is advised for adults 45 years or older. Some with risk factors such as family history or related health issues may start earlier. People who are blacks and Alaska Native have a higher risk and may also need earlier screening. 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 person has certain 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 take pictures of the colon and cancer:
    • CT scan, CT colonography
    • MRI scan
    • Transrectal ultrasound
    • PET/CT scan
  • 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 is done 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. This is 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

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 uses drugs to kill cancer cells. It may be 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.

Targeted Therapy

These medicines block tumors from growing and spreading. They may be used with other methods. These medicines are often not be used until cancer is in later stages.


Some changes in daily habits may lower 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.
  • If you drink alcohol, limit it to:
    • 2 drinks a day or less—if you are a man
    • 1 drink a day or less—if you are a woman
  • Keep your weight in a moderate range.

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.

This content is reviewed regularly and is updated when new and relevant evidence is made available. This information is neither intended nor implied to be a substitute for professional medical advice. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with questions regarding a medical condition.

Edits to original content made by Denver Health.