WEDNESDAY, Aug. 22, 2001 (HealthDayNews) -- Once is not enough when it comes to testing for colon cancer. In fact, even one type of test may not be enough, says a new study.
About 24 percent of people with early colon cancers or precancerous growths are missed by a one-time screening with either of the two most common tests. Repeat testing can save lives, says Dr. David Lieberman, chief of gastroenterology at the Portland Veterans Affairs (VA) Medical Center in Oregon.
"Our study provides data on how often colon cancer can be detected with existing screening methods," Lieberman says. "This study fills in some pieces of the puzzle that were not known before. We did not know how many patients screened with these tests would not have growths detected."
This study is reported in the latest New England Journal of Medicine.
Lieberman says colon cancer testing needn't be done that often, and a variety of tests are available. One option is a yearly at-home test that looks for blood in the feces; another test, called a sigmoidoscopy, is usually done every five years in a doctor's office and inspects the lower part of the colon. The accuracy of those two tests was the focus of his team's research.
Lieberman is more a fan of the colonoscopy, a procedure done in a hospital setting under light anesthesia, which looks at the entire colon. He says it should be done every 10 years, starting at age 50 or earlier and more frequently if there is a family history of colon cancer. Another option is a barium enema every five to 10 years.
"We know that in many circumstances, physicians do not talk to patients about screening for colon cancer, and that is a tremendous barrier to getting screening. For patients, it is not a test they really want even though they need it," Lieberman says.
The life-saving potential is great. Colon cancer, second only to lung cancer in incidence, will kill 55,000 of the 130,000 Americans who will get the disease this year. Early detection "is cost-effective in terms of what else we do in medicine and will save lives," Lieberman says.
Lieberman and his colleagues analyzed the results of colon cancer screenings for 2,885 apparently healthy volunteers, aged 50 to 75, at 13 VA medical centers. All underwent colonoscopy, while nearly 2,300 also had fecal occult blood tests. Most of the volunteers also had a sigmoidoscopy.
The fetal occult blood tests picked up only 24 percent of the intestinal polyps, growths that can become cancerous, that colonoscopy detected in the volunteers. For actual cancers, sigmoidoscopy detected 70 percent of those found by colonoscopy, while the combination of the fecal blood test and sigmoidoscopy raised that percentage to 76 -- meaning nearly a quarter of colon cancers would have gone undiagnosed.
The study also found that "combined screening appears to become less effective as we age," Lieberman says. "Older patients are more likely to develop growths in the upper part of the colon, growths that are not detected by sigmoidoscopy."
That finding reinforces Lieberman's support for colonoscopy. "It gives the reassurance of examining the entire colon and can be used to remove growths and polyps at the time the investigation is done," he says.
But colonoscopy has a down side, says Robert Smith, director of screening for the American Cancer Society. It is expensive, can cause physical damage, is not available to every primary physician and sometimes is not covered by medical insurance. He says the most important point regarding colon cancer is that everyone should have some sort of screening test.
"All of these tests vary in cost and efficacy, but all have been associated with a reduction in mortality," Smith says. The easiest option is the fecal occult blood test, which is inexpensive and can be done at home. He says it will have its share of misses, "but because colon cancers grow slowly, repeated screening over time has benefits." Each test has its advantages, while doing nothing has no advantage, he says.
What To Do
"The American Cancer Society recommends that everyone aged 50 and older, and younger people with a family history of colon cancer, should talk to the family doctor at the first opportunity about colorectal cancer screening," Smith says. "People should get the most thorough and accurate test that is available to them."
To learn about the different tests for colon cancer, go to Veterans Affairs Medical Center, San Francisco. And here's an explanation and drawing of how a colonoscopy is done.
For more information about colon cancer, its causes, prevention and treatment, visit the National Cancer Institute.
