New colon cancer tests helpful, but colonoscopy called best
February 24, 2014 12:00 AM
AP Photo/Given Imaging
Pillcam -- the new colonoscopy capsule.
By Mackenzie Carpenter / Pittsburgh Post-Gazette
Of all of life's necessary indignities, perhaps none is more dreaded -- and avoided -- than a colonoscopy to screen for early signs of colorectal cancer, the second most common cancer-related cause of death in the U.S.
It doesn't have to be because colon cancers can be caught early -- but many people are reluctant to undergo a time-consuming colonoscopy, which requires a day of cleansing the bowels and, then under partial anesthesia, submitting to a tube, called a colonoscope, that is moved up through the large intestine.
Researchers have been working to come up with alternatives, but even two new screening procedures won't serve as a viable substitute for the time-tested colonoscopy, which has a 98 percent success rate at detecting cancer, according to two Pittsburgh experts.
First, the Food and Drug Administration recently approved a new method of "capsule colonoscopy," using a camera inside a capsule that a patient swallows. It then moves through the entire colon, taking pictures that are uploaded to a computer for medical staff to examine for abnormalities.
Second, there's a new study that touts the benefits of a recently developed at-home, mail-in test that uses a stool sample to detect up to 79 percent of colon cancers.
So-called capsule cameras are already used for endoscopies -- in the upper end of the digestive tract -- and in the small bowel, but their batteries never lasted long enough to go through the entire length of the colon.
The new colonoscopy capsule changes that, but Paul Lebovitz, a gastroenterologist at Allegheny General West Penn Health System, remains skeptical.
The disposable camera capsule, for example, "is not directive. When you use a regular camera probe, you can stop, take a picture, or go back and look closely. The camera capsule is a lot less invasive, and that's a benefit, but it's unlikely to be as sensitive."
And if the camera does pick up on something, the patient must then come back anyway for a colonoscopy and biopsy to have the growth -- called a polyp -- removed. Almost all colorectal cancers begin as a small polyp, and if found and removed early, the cancer is eliminated.
It's unlikely the procedure will be covered by insurers immediately, he said, until more research is done.
The capsule's manufacturers say they are working on technology that would enable removal of a polyp or a cancerous tumor in sequence with the procedure, but for now, capsule colonoscopies "will only help visualize what's going on," added Edward Chu, a deputy director of the University of Pittsburgh Cancer Institute who has done extensive research into colon cancer. "You still have to go in to confirm whether a growth is abnormal or not and do a biopsy."
Capsule endoscopies, and virtual colonoscopies have been in use for several years, and they might be useful in getting an individual comfortable with the idea of screening, "but I would say the colonoscopy still remains the gold standard for early detection. And for colon cancer, if you can detect it early in the form of a polyp, there's a 95 percent cure rate."
People at normal risk for colorectal cancer, usually those over age 50, are urged to be screened regularly until age 75, although nearly a third of American adults over age 50 have not had the tests done, according to the Centers for Disease Control and Prevention.
Dr. Chu noted that the reluctance to undergo colonoscopies is more pronounced among women, who might be focused more on breast cancer, even though they are at equal risk with men for cancer of the colon.
What of the new stool sample test, known as a fecal immunochemical test or "FIT"? It detects DNA mutations by employing specific antibodies that bind the human blood in a patient's stool. A study published in the Annals of Internal Medicine found that those tests detected colorectal cancer 79 percent of the time. A previous test, the fecal occult blood test, was far less sensitive and required three consecutive samples instead of one.
The FIT tests are beginning to be covered by the insurance industry as part of a regular screening for patients over age 50 at their annual physical.
"The attractive piece for this is a noninvasive approach to look at DNA genes that get mutated when cancer develops," said Dr. Chu. "One still has to go in and do a colonoscopy to look at where the tumor is located. It's not definitive and it can't identify the specific location, but it's a good test for initial screening."
Still, while the FIT has picked up cancers 79 percent of the time, "what about the other 21 percent?" asked Dr. Lebovitz, noting that other screenings besides colonoscopy now available include CAT scans, flexible sigmoidoscopies -- which survey less terrain -- and virtual colonography, which uses computers and X-rays to look inside the bowels.
Despite the FIT's limitations, it has its uses, he said.
"I do think it will come to Pittsburgh, it will eventually be covered by insurance and many primary physicians will incorporate it into practice. Anything we can do to draw people into any of the modalities of screening is well worth it."
Mackenzie Carpenter, firstname.lastname@example.org, 412-263-1949. On Twitter @MackenziePG.
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