A colonoscopy is an effective procedure used to combat colorectal cancer, but it may not be quite as effective as previously thought, suggests a new Canadian study.
While the procedure does a good job of detecting early signs of disease to the left side of the colon, or large intestine, it is not as effective at detecting potential problems on the right side of the colon.
“The good news is that we found colonoscopy is effective. It is still one of the best screening tests available for any cancer that we have,” said study author Dr. Nancy Baxter, a colorectal surgeon with St. Michaels Hospital in Toronto.
“The bad news is, it’s not perfect,” she added. “It does not appear to be as effective at detecting growths on the right side of the colon as detecting them on the left.”
Colonoscopy which involves inserting a tube into the rectum to check for potentially cancerous growths, prevent an estimated 60 to 70 percent of deaths from colorectal cancer, not 90 percent as previously thought, wrote David Ransohoff, M.D., a professor of medicine at the University of North Carolina at Chapel Hill, in a commentary on the study.
Researchers followed 10,000 people in Ontario, Canada, who have been diagnosed with colorectal cancer between 1996 and 2001 and had eventually died from the disease by December 2003. The study compared each patient with 5,000 other healthy individuals of similar background who did not die of colorectal cancer.
Slightly more than 700 of the cancer patients – or 7 percent – had undergone a colonoscopy.
The American Cancer Society ranks colorectal cancer third in the U.S. in terms of cancer diagnoses among men and women. 153,000 cases of colon and rectal cancer are expected to be diagnosed, this year. And, about 50,000 of them will die from the disease.
Dr. Judith Collins, section chief of gastroenterology at the VA Medical Center in Portland, cautions that while there are apparent limitations highlighted in the new study, colonoscopy is still the golden standard for detection of colorectal cancer.
“Colorectal cancer is totally preventable,” she said. “So whether screening for it results in 60 or 90 percent reduction in death, the bottom line is, there is no other cancer that we can see this well, and colonoscopy most certainly helps reduce mortality. Several variables show the test is not perfect, but it is still a very good test.”
The editorial titled, “How Much Does Colonoscopy Reduce Colon Cancer Mortality?” is published online in the December 16 issue of the Annals of Internal Medicine.
The U.S. Food and Drug Administration will be adding “black-box warnings” on two prescription drugs used to cleanse the bowel before a colonoscopy because they may cause kidney damage.
The black-box warnings, the agency’s strictest warning, will apply to OsmoPrep and Visicol -- prescription oral sodium phosphate (OSP) products. #