Recent studies in the New England Journal of Medicine offer compelling reasons to mothball the flexible sigmoidoscopes widely used for colorectal cancer screening in physician offices across the country in favor of colonoscopes, which are more likely to be found in hospitals and outpatient clinics.
One of the studies found that sigmoidoscopy may miss as many as one-third of all cancers or precancerous growths.
Another study concluded that if patients were given a clean bill of health based on a sigmoidoscopy of the lower section of the colon, about half the cases of cancer or precancerous lesions in the upper reaches would be missed.
Prescribing the less invasive sigmoidoscopy over the more costly colonoscopy has been compared to ordering a mammogram for only one breast.
But don't count sigmoidoscopes out just yet. Anything is better than nothing when it comes to fighting one of the most preventable of cancers, according to some experts.
"The truth is most places aren't doing any (colorectal cancer) screening at all," says David Lieberman, M.D., the lead author of one of the NEJM studies and chief of gastroenterology at Oregon Health Sciences University and the Portland (Oregon) VA Medical Center. "It's appallingly low."
What is the difference between a sigmoidoscope and colonoscope? Literally, 95 centimeters.
That's according to Joseph Oberle, gastrointestinal product director of Olympus America, Melville, N.Y., a leading manufacturer of gastrointestinal endoscopy products.
Other differences between the two focus on the costs involved and the expertise required to use them, Oberle says.
Both scopes are designed to examine the colon, 99% of the time with the help of a computer chip that transmits the image of the patient's colon to a video screen.
But a sigmoidoscope includes a flexible tube that is 73 centimeters long and probes as far as the descending colon. The insertion tube on the colonoscope is 168 centimeters long, giving doctors the ability to examine the colon's entire length.
Typically, a flexible sigmoidoscopy requires little or no sedation and can be performed in a doctor's office by a primary-care physician, physician's assistant or nurse practitioner. The procedure generally takes no more than 30 minutes. On average the charge for the procedure ranges from $200 to $250, with reimbursements coming in at anywhere from $85 to $130, Oberle says.
The longer insertion tube complicates the colonoscopy, according to Oberle. Patients typically require mild, "conscious" sedation, and specialists like to perform the procedure in a facility where there is monitoring equipment available.
Charges for a colonoscopy range from $1,000 to $3,000, with reimbursements coming in at $400 to $500, Oberle says.
Colorectal cancer is the third most common cancer in men and women and the second leading cause of cancer death after lung cancer. About 130,000 people will be diagnosed with colorectal cancer this year, and an estimated 55,000 people will die from it.
Most guidelines, including those followed by Medicare, reserve colonoscopies for patients who are at the highest risk of contracting colorectal cancer. For patients over the age of 50 with no symptoms or risk factors, Medicare will reimburse a yearly fecal occult blood test for detecting small amounts of blood; then once every four years Medicare will pay for a sigmoidoscopy or that old standby, the barium enema.
The barium enema test is falling into disfavor as well, thanks to Sidney Winawer, M.D., the Paul Sherlock chair in gastroenterology at 450-bed Memorial Sloan-Kettering Cancer Center in New York.
In a study published in the NEJM in June, Winawer details a head-to-head comparison between the barium enema test and colonoscopy. In short, colonoscopy blew the barium enema out of the water.
Yet Winawer, who was part of a 1993 study that gave researchers the first strong evidence that removing precancerous polyps may prevent colorectal cancer, is by no means ready to wash his hands of sigmoidoscopes. Although the scientific evidence is mounting, more long-term, large-scale studies are needed, he says.
"They are limited studies, and there is a risk because colonoscopy is more invasive, requires highly trained individuals and is more costly," Winawer says. "There is more and more evidence that this approach is promising, but we need to be on firm ground before making this public policy because we are talking about 50 million to 60 million people over the age of 50 in this country."