More Evidence That Colonoscopy Saves Lives

Several studies have shown that colon cancers diagnosed through routine screening are less likely to cause death. A new study finds that this is true even for cancers diagnosed at the same stage. The study included almost 1,100 people. Cancers found by a routine screening test called a colonoscopy were usually diagnosed at an earlier stage than those found because of symptoms. Those found because of symptoms were 2 to 3 times as likely to spread as those found through screening. And cancers diagnosed at the same stage were more likely to be deadly if they were found because of symptoms. The New England Journal of Medicine published the study. HealthDay News wrote about it June 19.

By Robert H. Shmerling, M.D.
Harvard Medical School

What Is the Doctor's Reaction?

For more than a decade, colonoscopy as a screening test for colon cancer has been recommended for every adult. For most people, tests should begin at age 50. If the results are normal, a repeat test is recommended every 10 years until age 75.

Earlier or more frequent screening may be advised for some people. Reasons for more frequent tests include factors that increase colon cancer risk (such as a strong family history of the disease) or abnormal colonoscopy results.

The test is recommended for two reasons:

• To detect pre-cancerous growths that can be removed before cancer develops
• To detect colon cancer at a curable stage

Well-designed studies have shown that colon cancers found during a screening colonoscopy are less likely to be advanced when first diagnosed than cancers found because of symptoms (such as bleeding). In fact, screening colonoscopies are thought to have contributed to a drop in U.S. colon cancer rates in the last 10 years.

Now a new study suggests that colonoscopy may be even better than we thought.

The study included more than 1,000 people diagnosed with colon cancer. About 20% were diagnosed after a screening colonoscopy. The rest were diagnosed in other ways. For example, they may have had tests because of bleeding or abdominal pain.

Some of the findings were expected:

• When the diagnosis of colon cancer occurred after a screening colonoscopy, the disease was less advanced than for those not screened. For example, those who were screened had half the rate of metastatic disease (cancer that had spread outside the colon) compared with those in the unscreened group.
• A return of colon cancer after treatment was less common among those screened.
• People who were screened lived longer.

The surprising finding was that colon cancers diagnosed by screening has less spread of the disease over time. This occurred even among people who had colon cancers of similar stages -- whether early or late. People diagnosed through screening also lived longer. This is a remarkable finding. It's yet one more reason to encourage screening colonoscopies.

What Changes Can I Make Now?

You can take measures now to lower your risk of colon cancer. Besides having screening colonoscopies, experts estimate that a large number of cases of colon cancer can be prevented by:

• Eating more fruits, vegetables and whole grains
• Getting regular exercise
• Limiting red or processed meats and saturated fat in your diet
• Not smoking
• Drinking only moderate amounts of alcohol

If you are at least 50 years old and you don't have regular screening colonoscopies, talk to your doctor. Ask about when you should start having them and how often they should be repeated.

Unfortunately, many people do not have colonoscopies as recommended. There are several reasons for this:

• The preparation (often called "the prep") -- Getting the colon "cleaned out" so it can be inspected well means not eating solid food for a day or two. You also have to take a series of laxatives. For many people, this is the most unpleasant part of the test.
• Discomfort -- Some people feel cramping or pain during the test. But severe pain is quite unusual.
• Risk -- About 1 or 2 people out of 1,000 will have a major complication, such as a puncture of the bowel wall.
• Cost -- A colonoscopy can cost $1,000 or more, though health insurance usually covers it. Many people also have to miss work to get the test done.
• Too few doctors -- In many places, there are not enough qualified doctors to perform the test.

Even so, having a colonoscopy every 10 years seems a small price to pay for the benefits it provides. Other, "second choice" screening tests also are available. They include a rectal examination, a test of the stool for blood, or a CT scan.

What Can I Expect Looking to the Future?

You can expect to hear about more studies that confirm and extend the findings of this latest research. Future studies may clarify why people with colon cancer diagnosed by a screening colonoscopy have better outcomes than those with similar tumors found without screening.

Perhaps people who have screening colonoscopies have better overall health. Maybe they have healthier lifestyles or better access to health care than people who don't get screened. Or it may be that even when the stage of disease is similar, tumors that cause symptoms (such as bleeding or pain) are more aggressive.

For many tests, early research on a small, select group of subjects produces dramatically positive results. But often later studies of "real life" patients yield more modest benefits. For screening colonoscopies, the opposite seems to be happening: The more it's studied, the better it looks. This new report is just the latest example.