Two large-scale studies by separate research teams looked at colon cancer screening tests and how they are used by doctors. One team compared the effectiveness of two types of fecal occult blood tests (FOBT), used to detect blood in the stool. The presence of blood in the stool can be an indication of colon cancer. The other group reviewed how doctors actually use FOBTs in their practices.
The researchers found that one test is better than the other, but it's not being used as often as it should be.
The First Study: Comparing Tests
The study included 2,665 people between the ages of 50 and 75 years from 13 different Veterans Affairs Medical Centers. Nearly all of the participants were men, and none had symptoms of colon cancer.
All of the study volunteers had a physical exam and a test that used a single stool sample. Then they were asked to provide fecal samples for a six-sample home-collected test. Finally, they all had colonoscopies, a procedure in which a thin, flexible tube with a light and camera is inserted into the rectum so the doctor can view the inside of the colon. This helped determine the accuracy of the other two tests.
In total, 284 people had "serious" polyps, which often turn into cancer, notes study author Dr. Judith Collins, section chief of gastroenterology at the Veterans Affairs Medical Center in Portland.
The six-sample home test was far superior, detecting 23.9% of likely cancers compared with only 4.9% detected by the single-sample office test.
"This is an education issue for both patients and physicians," says Collins. She thinks many doctors use the office test because they believe it is as reliable as the six-sample test. Patient compliance is also an issue with the home test, she adds.
The Second Study: Doctors’ Decisions
In another study, researchers interviewed more than 1,100 primary care physicians about their colon cancer screening practices. They also interviewed more than 11,000 people older than 50 years to find out what screenings had been performed.
Approximately 25% of the patients reported having a fecal occult blood test. One-third of those had the in-office test only. Most of the doctors—90%—said they used fecal occult blood testing at least once a month, and one-third said they relied only on the in-office test.
of the patients, 10% said they had abnormal fecal occult blood tests, but fewer than 50% were referred for further testing,
One of the reasons doctors still rely so heavily on the single test is because there had been no good comparison of the tests until now, says Dr. Harold Sox, editor of the Annals of Internal Medicine.
"As far as I know, this is the first very high-quality study that shows the poor performance of the single-sample test," Sox notes. "I hope that when doctors read about this study, they'll realize that the single sample in-office approach isn't the right way to go."
"Colon cancer is one of the primary causes of death from malignancy. After the age of 50, it's important to screen for cancer and polyps," says Sox. "Talk about it with your doctor and don't settle for the single-sample test done in the office. Insist upon the six-sample fecal occult blood test."
While the six-sample test was better at identifying precancerous polyps than the single test, screening guidelines recommend not relying on either test alone.
The American Cancer Society (ACS) recommends an annual fecal occult blood test, a colonoscopy every 10 years and a flexible sigmoidoscopy every five years for people older than age 50.