Colon cancer study backs blood stool screening test

Although colon cancer screening is recommended by many organizations, less clear is which method is best to detect tumors and precancerous lesions.

A new study in the New England Journal of Medicine suggests that a relatively inexpensive and non-invasive test may be just as effective as a colonoscopy.

Meanwhile, a 23-year study, also published in the journal, has confirmed that removing precancerous polyps, known as adenomas, during a colonoscopy can reduce the risk of death from colorectal cancer by half.

Based on the results, "an appealing concept would be to use colonoscopy as a triage screening test, offering it once for everybody at 60 years of age" and using it to classify people into high- and low-risk categories, Dr. Michael Bretthauer of Oslo University Hospital and Dr. Mette Kalager of Telemark Hospital, both in Norway, wrote in an editorial in the journal.

Low-risk people would not need further screening while those with adenomas would be evaluated regularly.

One in 20 Americans will develop colorectal cancer. About 140,000 cases are diagnosed in the United States each year, resulting in about 49,000 deaths, according to the National Cancer Institute. It is the third most common cancer worldwide.

The U.S. Preventive Services Task Force, a government-backed agency, recommends screening for people age 50 to 75 years by one of three methods: a colonoscopy every 10 years; annual stool testing; or a less-thorough look into the colon (known as flexible sigmoidoscopy) every five years in conjunction with stool testing every two to three years.

People often find the tests unpleasant. For example, in the new study that compared stool testing with colonoscopy, only 34 percent went along with stool testing. The participation rate was even lower when colonoscopy was offered, even though doctors can use it to cut away those suspicious precancerous adenomas.

Several tools may be used, either alone or together, to screen for colon cancer:

The first method is a stool test that checks your bowel movements for blood.

- Polyps in the colon and smaller cancers often cause small amounts of bleeding that cannot be seen with the naked eye.
- The most common method used is the fecal occult blood test (FOBT). Newer stool tests are called the fecal immunochemical test (FIT) and stool DNA test (sDNA).

The second method is a sigmoidoscopy exam.

- This test uses a flexible small scope to look at the lower part of your colon. Because it only looks at the last one-third of the large intestine (colon), it may miss some cancers.
- A stool test and sigmoidoscopy should be used together.

The third method is a colonoscopy. A colonoscopy is similar to a sigmoidoscopy, but the entire colon can be viewed. You will usually be mildly sedated during a colonoscopy.