Question from: 8/18/97 by Todd L. Sack, M.D.
The Borland-Groover Clinic, Jacksonville,FL

Answer: Gastroenterologists (digestive disease specialists) try to decide for each individual whether that person is at normal or increased risk of developing colon cancer. Several factors are considered here, such as age, smoking history, history of other cancers, history of medical illnesses such as ulcerative colitis which increase the colon cancer risk, and family history. I'll deal with family history here.

A family history of colon cancer is of increasing concern if the relative with cancer is young (under 55) at the time of the cancer diagnosis, a close relative (parent, sibling, child), and if numerous (many relatives with cancer). If the relative has polyps but not cancer, this is of less concern, and especially so if the polyps were all small (under 1cm) and if none were adenomatous (precancerous).

In normal-risk people, physicians (and our cancer societies and government) advise the use of two tests: the test for detection of blood in bowel movements (feces,stools) and the flexible sigmoidoscopy test. Starting at age 50, 3 stool tests are submitted to a laboratory annually; if blood is found, a colonoscopy is performed to examine the entire colon with an instrument. Flexible sigmoidoscopy is a quick, minimally uncomfortable test done in the doctor's office at age 50 and every 3 - 5 years thereafter. If polyps are seen, a full colonoscopy is performed (see below). This strategy, in several giant studies, has been demonstrated to save lives (and studies suggest this is less expensive for saving lives than mammography).

High-risk individuals should have their entire colon examined. The recommended method is colonoscopy because it is thorough and allows the gastroenterologist to remove any polyps or small cancers found. This is an outpatient procedure which takes 30-60 minutes and for which intravenous sedation is provided so that pain is unusual. It is quite expensive, however, and there is an increased, though small, risk of significant complications. An alternative is the combination of flexible sigmoidoscopy and a barium enema x-ray study--less accurate but much less expensive.

In regards to the questioner, the answer depends on his personal risk factors, factors related to his father's tumor, the questioner's ability to pay for any tests, and his own attitude towards risk. If all this irons out to his being of normal risk, he should wait until age 50 to begin routine screening (stool tests and flexible sigmoidoscopy). If his risk is more worrisome, he should at age 50 have colonoscopy or the combination of flexible sigmoidoscopy and barium enema xray. If his risk is quite high, colonoscopy should begin at age 40 (for some families, at age 20!) and be repeated each 10 years.

This is a simple reduction of literally thousands of research papers on this topic, and other experts might have a somewhat different answer. The questioner should speak with his own primary care physician or gastroenterologist before deciding.

Author: Todd L. Sack, M.D.
The Borland-Groover Clinic, Jacksonville,FL

The following excerpts were taken from the "Guide to Clinical Preventive Services", Second Edition. (

"The U.S. Preventive Services Task Force is a Government-appointed expert panel that worked from 1984 to 1989 to develop recommendations for primary care clinicians on the appropriate content of periodic health examinations. The recommendations were based on a systematic review of approximately 2,400 published papers reporting the results of relevant clinical research. The 5-year task force project concluded in 1989 with the release of its final report, the Guide to Clinical Preventive Services. The Guide evaluated the clinical effectiveness of 169 preventive services-- screening tests, counseling interventions, immunizations, and chemoprophylactic regimens--and provided age-, sex-, and risk factor-specific recommendations about services that should be considered for periodic health examinations."

"In July 1990, the Task Force was reconstituted by the Department of Health and Human Services to continue and update these scientific assessments of preventive services. The charge of the Task Force was to evaluate the effectiveness of clinical preventive services that were not previously examined; to re-evaluate those that were examined and for which there is new scientific evidence, new technologies that merit consideration, or other reasons to revisit the published recommendations; and to produce the Guide to Clinical Preventive Services, 2nd Edition."

Examples of Preventive Services Recommended for Routine Use

"Screening for Colorectal Cancer

Condition: Colorectal cancer causes 55,000 deaths each year and is the second most common form of cancer in the U.S.

1995 Recommendation: Screening for colorectal cancer is recommended for all persons aged 50 and older, using sigmoidoscopy, annual fecal occult blood testing, or both. The optimal interval between sigmoidoscopic examinations is not established; a 10-year interval may be adequate. "

Editor's Comments:

As a personal note, I do not feel the recommendations of the U.S. Preventive Services Task Force are quite thorough enough for all situations. We try to individualize our advice based on the information Dr. Sack recommended gathering above.

Colon cancer is essentially a preventable disease in most cases. A diet high in fiber and low in fat is very important. There is mounting evidence that taking an aspirin a day can reduce the incidence of both colon polyps and colon cancer. There are no symptoms when a polyp has formed in the colon. Each adenomatous polyp has approximately a 20% chance of turning cancerous over time!

Here's the bad news. The only way to detect precancerous polyps and help prevent the development of colon cancer is to go looking for them inside the colon. No, a blood test can't do this for you (nice try!) and the occult blood cards will only be positive if there is a bleeding lesion in the gastrointestinal tract (most polyps will not bleed in the early stages).

In my clinical practice, I tend to recommend a full colon exam (i.e. colonoscopy or a barium enema with or without flexible sigmoidoscopy ) every five to ten years starting at age 50 for normal risk individuals. For high risk individuals, I tend to institute a screening program at a younger age (preferably with colonoscopy) and screen more often (every 5 years).

Charles H. Booras, MD

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