Johns Hopkins Health Alert
Research Update on Colon Cancer Screening Tests
- How often should you have a colonoscopy for colon cancer? A large long-term study shows a 10-year interval is safe in most cases.
A Canadian study reported in the Journal of the American Medical Association confirms that a 10-year interval between colonoscopy screenings is appropriate for those who have had one negative procedure.
Ten-year intervals have long been recommended for colon cancer screening, but there has been limited evidence to show whether there are benefits to more frequent colonoscopies in this group. Researchers studying cancer risks at the University of Manitoba looked at records for nearly 36,000 patients who had negative screenings between 1989 and 2003. They compared the incidence of colorectal cancer in this group with that in the provincial population. These data are simple to obtain in Manitoba, where the government pays all health care costs and keeps all records by patient ID numbers.
Researchers found that the risk of developing colon cancer within less than 10 years of a negative colonoscopy was very low and remained lower beyond that time. In fact, one year after a negative screening, the risk of developing colon cancer was 31 percent lower than the risk among the general population. At 10 years, the risk of developing colon cancer was 72 percent lower. One anomaly: When people in the colonoscopy group developed cancer, tumors were significantly more likely than usual to develop in the right side of the colon (47 percent vs. 28 percent in the general population). Evidently early detection methods in that area need improvement.
- New research shows that while more Americans are being tested for colorectal cancer, follow-up lags.
Public campaigns have raised awareness about colorectal cancer and the importance of screening. But a Veterans Administration (VA) study showed that nearly half of those who tested positive on an initial colorectal screening test didn’t get a follow-up colon cancer examination.
Researchers reviewed VA records for nearly 40,000 people who qualified for colorectal cancer screening and found that about 61 percent were screened with a fecal occult blood test (FOBT). They then compared test results and follow-up visits for six months after the colorectal tests. Of those whose FOBT results were positive, 59 percent received a follow-up colonoscopy or barium enema screening -- but 41 percent had no follow-up at all. Nothing about the patients themselves seemed to predict who would have follow-up tests.
It’s standard medical practice after a positive FOBT to follow up with a colonoscopy or barium enema. The VA’s screening rates are significantly higher than the national average. Its lack of follow-up shows a need for more focus on the entire screening and diagnostic process, the researchers wrote. If your FOBT is positive, ask for follow-up even if your doctor does not mention it. This research was reported in the journal Diseases of the Colon and Rectum .
Posted in Colon Cancer on July 24, 2007
Reviewed June 2011
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I am an 82 yr old male and in good health. I have had a colonoscopy every 3 yrs for the past 15 yrs. Each time they found a benign polyp. I am due for another colonoscopy 4/09 but wonder if it is really necessary. A friend had it done and the colon was penetrated. He had to have an operation to repair the colon and ,in the meantime, had to wear a bag. I'm considering a " stool DNA" test being offered by a company called DNA direct. They state that the American Cancer Society " has recommended stool DNA testing as an option to consider for average risk people screening for colon cancer " I'm wondering if you have an opinion as to whether a person my age and condition should go for the "stool DNA" test- first- and then follow up with a colonosocopy only if the stool DNA test is "positive" - or - do you recommend going ahead with the colonoscopy anyway. Thank you for your help -- A Mainiac
Posted by: mainiac | October 15, 2008 4:11 PM