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While more than 142,000 people in the United States will find out they have colorectal cancer this year, with early detection it is one of the most treatable cancers.

Colon Cancer

Most colorectal cancers begin with benign growths or polyps in cells lining the colon. A polyp is a growth that projects from the lining of the intestine or rectum.

Polyps are usually noncancerous. They may cause painless rectal bleeding or bleeding not apparent to the eye.

These growths can become cancerous, invading the colon wall and eventually moving into blood vessels and spreading to other body areas.

Slow growth

It usually takes about five years for a polyp to reach ½-inch in diameter, and an additional 5 to 10 years for a ½-inch polyp to turn cancerous. Symptoms may not show up for another 5 to 10 years, often too late to cure.

Common symptoms

Frequently there are no symptoms. But the following changes MIGHT indicate colon cancer:

  • A change in bowel habits
  • Narrower than normal stools
  • Blood in the stool, dark stool, or rectal bleeding
  • A feeling that the bowel doesn't empty completely
  • Abdominal discomfort, pain, or cramps
  • Unexplained anemia
  • Unintended weight loss

Cancer detection

"Screening is the best way to find polyps before they become cancers, or to find colorectal cancers early," says colon and rectal surgeon Samuel Oommen, MD, on staff at John Muir Health.

Tests that find polyps and sometimes cancer include flexible sigmoidoscopy, double-contrast barium enema, colonoscopy, and CT colonography (virtual colonoscopy). These tests look at the colon with a scope inserted in the rectum or with x-rays.

Tests that mainly find cancer examine stool, or fecal matter, and include the fecal occult blood test, the fecal immunochemical test, and the stool DNA test. These tests are easier to do but less likely to detect polyps.

The American Cancer Society (ACS) recommends both kinds of tests if they are available to you and you are willing to have them – although the ACS prefers tests that find polyps before they become cancerous.

ACS schedule

The American Cancer Society recommends that average-risk adults should begin colorectal cancer screening at age 50, utilizing one of the following seven options for screening:

  • Annual fecal occult blood test (FOBT) or fecal immunochemical test (FIT)
  • Stool DNA test (sDNA), interval uncertain
  • Flexible sigmoidoscopy every 5 years
  • Colonoscopy every 10 years
  • CT colonography (virtual colonoscopy) every 5 years
  • Double-contrast barium enema every five years.

Persons at high risk need earlier and more frequent screening. If your doctor finds polyps with flexible sigmoidoscopy or a barium enema, he may perform a colonoscopy to remove the polyps and to make sure other polyps or cancer are not present.

Fecal occult blood test

You can easily do this test at home with one of several convenient methods of collecting a small stool sample. The test requires several samples from consecutive bowel movements and detects blood usually not visible to the eye, by chemical means.

Flexible sigmoidoscopy

A trained primary care physician can perform a flexible sigmoidoscopy. It takes only 10 to 20 minutes and does not require sedation.

The procedure can detect about two-thirds of polyps and over half of colorectal cancers.


Colonoscopy provides visualization, biopsy, and removal of polyps. The doctor will examine the colon lining by using a lighted, flexible tube and inserting it through the rectum.

"Colonoscopy is done under intravenous sedation, which makes the procedure comfortable for the healthy patient," says gastroenterologist Will Lane, MD, on staff at John Muir Health.


You may help prevent colorectal cancer if you:

  • Stop smoking
  • Take daily calcium supplements. (Men should limit calcium intake to less than1500 mg. a day because of an increased risk of prostate cancer.)
  • Lose weight if obese
  • Exercise daily
  • Eat lots of fruits and vegetables
  • Limit your consumption of alcohol and red meat
  • Get screenings at appropriate intervals

Brighter future

"Mortality rates from colon cancer have dropped since 1991, probably due to increased screenings and newer diagnostic and therapeutic technologies," Dr. Oommen notes.

The Centers for Disease Control and Prevention urge everyone over 50 to have their colons checked. Consult with your physician for the screening option best for you.