October 1, 1999

Screening for Colorectal Cancer in Women: Not Just a Man's Disease

There is an odd perception that colorectal cancer (CRC) is a man's disease. It is not. Women get CRC in almost the same numbers as men, at the same ages as men and require the same screening as men. Yet women are not being screened at the same rates as men. One study, for example, reported that 41.9% of men and 32.9% of women equal to or over the age of 50 said that they had ever had a proctoscopic exam, one of the major screening procedures.

In 1999, the American Cancer Society predicts that 129,400 Americans will be diagnosed with colorectal cancer, 62,300 men and 67,000 women. The ACS also predicts that 56,600 Americans will die from colorectal cancer, 27,800 men and 28,800 women.

The Benefits of Screening
All these deaths do not have to happen to either men or women. In the past twenty years we have learned a great deal about the biology of CRC. Risk factors have been identified. Technology has advanced and screening procedures have been developed. At last, we are able to say that preventive screening decreases the death rate from CRC. Better yet, we have found that if adenomatous polyps, the precursor lesions of CRC, are found and removed at screening, CRC will be prevented entirely.

Strong efforts are now underway to encourage the habit of screening. The precursor lesion of CRC, the adenomatous polyp, is a benign growth, which is found in increasing numbers as people pass age 40. The cancer rate begins to rise after age 50. Not all of these polyps will develop into cancers. Current estimates are 2.5/1000/year but it is impossible to predict whether any given adenomatous polyp found will develop into a cancer. Larger polyps (over one centimeter) and those with abnormal cells (dysplasia) are more likely to become malignant.

Risk Factors
Some factors will increase risk for polyp and cancer development. First of all, polyps increase in frequency with age, hence the new guidelines published by the American Cancer Society to start screening at age 50. Basically, there are three risk levels: average, moderate and high. Seventy to 80% of CRC cases develop in the average risk category — people who are 50 and over. Ten to 15% of cases occur in people who have a personal or family (first degree relative — parent, sibling, child) history of CRC or polyp and are in the moderate risk category. Five to 10% of CRC cases are in the high-risk group — people with inflammatory bowel disease (ulcerative colitis or Crohn's disease) or one of the rare familial cancer or multiple polyp conditions. The high-risk patients tend to be under specialty care and management. The primary care physician must concentrate on the patients in the moderate and average risk groups that account for 90-95% of the cancers that develop.

Screening Protocols
It takes about 10-15 years for an adenomatous polyp to progress to a cancer. Screening procedures and intervals are geared to take this biology into account. If any first degree relatives have had CRC, subtract 10 years from the age that the youngest relative was diagnosed and start screening then. Or you can just start screening at age 40. If the relative got the cancer at an older age, over 60, there is probably not much increase in risk and you can start screening at the same age, 50, as the average risk person.

Regardless of the age you start the screening, the recommendations are: (1) yearly fecal occult blood test (FOBT) and flexible sigmoidoscopy every five years, (2) colonoscopy every 10 years, or (3) air contrast barium enema (ACBE) every 5-10 years with flexible sigmoidoscopy.

For the average risk patient, the doctor asks the person to provide a sample of their stool, which the doctor checks for hidden blood. This test is called the FOBT (fecal occult blood testing, three-day card). Even if no blood is detected, the person should next have a flexible sigmoidoscopy (flex sig) just to make certain no cancer is lurking. The scope is inserted into the rectum to view the lower part of the colon. If the doctor sees no signs of disease, the person should return for an FOBT every year and a flexible sigmoidoscopy every five years.

If the FOBT test is positive or the patient is in the moderate or high-risk category, colonoscopy is the procedure of choice. The colonoscope is sufficiently long to see the lining of the entire colon. If the entire colon is negative for polyps, a repeat colonoscopy is not considered necessary for 10 years.

Air contrast barium enema (ACBE) is less commonly done for screening but is helpful in cases where the scopes cannot be fully inserted into the colon. A frequent reason for this problem is pelvic surgery, commonly ovarian surgery or hysterectomy/oophorectomy in women, which sometimes causes surgical scar tissue to attach and tighten around the colon, thus preventing easy viewing The ACBE can easily pick up constricting lesions and large masses but is less sensitive in picking up small polyps.

There is now clear evidence of a decreased death rate in patients who have been screened with FOBT and/or rigid sigmoidoscopy. Studies are underway to validate that flexible sigmoidoscopy and colonoscopy are beneficial. One thing we do know is that these latter two procedures are "downstaging" CRC so that it is being found in the earlier, more curable stages.

Insurance Considerations
As Medicare has begun to cover screening procedures, other insurers have followed suit. Now many plans will allow colonoscopy to screen patients with a family history. Detection of blood in the stool requires colonoscopic investigation.

My Personal Favorite Screening Exam
Colonoscopy is my favorite. It's the most expensive, $1000 and up, but not painful because you are sedated and, most importantly, allows your doctor to see the whole colon. Best of all, if the test is negative, you don't have to check again for 10 years. And, if polyps are found, they can be removed at the same time.

Preparation for the colonoscopy is very important. The colon has to be completely clean. Tell your doctor if you suffer from constipation so that you can be put on a special dietary regimen several days before the colonscopy. Why am I telling you all this? Because women tend to be more constipated than men (don't ask me why).

Women, like men, get colorectal cancer. Screening for CRC, for both men and women, helps identify precancerous lesions at an earlier, more curable stage. Though sometimes complex and difficult, CRC screening is making a positive difference.
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