Colonoscopies May Not Have 'Blind Spot' After All: MedlinePlus

Colonoscopies May Not Have 'Blind Spot' After All
New study finds procedure can detect cancers on right side of colon, too

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MONDAY, Jan. 3 (HealthDay News) -- In addition to reducing the risk of cancer on the left side of the colon, new research indicates that colonoscopies may also reduce cancer risk on the right side.

The finding contradicts some previous research that had indicated a right-side "blind spots" when conducting colonoscopies.

However, the right-side benefit shown in the new study, published in the Jan. 4 issue of the Annals of Internal Medicine, was slightly less effective than that seen on the left side.

"We didn't really have robust data proving that anything is very good at preventing right-sided cancer," said Dr. Vivek Kaul, acting chief of gastroenterology and hepatology at the University of Rochester Medical Center. "Here is a paper that suggests that risk reduction is pretty robust even in the right side. [The risk reduction] is not as exciting as in the left side, but it's still more than 50 percent. That's a little hard to ignore."

The news is "reassuring," agreed Dr. David Weinberg, chairman of medicine at Fox Chase Cancer Center in Philadelphia, who wrote an accompanying editorial on the finding.

Though no one study ever provides definitive proof, he said, "if the data from this study is in fact true, then this gives strong support for current guidelines."

The American Cancer Society recommends that normal-risk men and women be screened for colon cancer, starting at age 50. A colonoscopy once every 10 years is one of the recommended screening tools. However, there has been some debate as to whether colonoscopy -- an invasive and expensive procedure -- is truly preferable to other screening methods, such as flexible sigmoidoscopy.

Based on a review of medical records of 1,688 German patients aged 50 and over with colorectal cancer and 1,932 without, the researchers found a 77 percent reduced risk for this type of malignancy among people who'd had a colonoscopy in the past 10 years, as compared with those who had not.

The lion's share of the benefit was seen for left-sided cancers, although there was still a 50 percent reduction on the right side (only 26 percent among those aged 60 and younger).

No one knows why colonoscopy seems to be superior in detecting problems on the left side of the colon.

"There are a number of potential reasons," Weinberg said. "It may be that the biology is conspiring to make it harder. [The polyps] look different, grow differently. Also, the quality of the laxative preparation tends to be less effective than on the other side so you might be more likely to miss something."

Then there's the issue of who's doing the test, which might be key.

"Colonoscopy performed by an experienced gastroenterologist or endoscopist probably mitigates the miss rate on the right side," Kaul said. "Myself and a lot of colleagues spend a lot of time in the right colon going back and forth, back and forth. You cannot just whip the scope out from there. You've got to spend time."

Weinberg added that the number of colonoscopies a person has performed also might make a difference. "This is a very good screening mechanism against a very common cancer," he said. "It's not perfect, but it works a lot better than nothing."

Kaul agreed. "This paper adds a little more bite to the argument that, yes, colonoscopy is an invasive procedure. Yes, it is somewhat costly compared to some of the other available options. But, it probably is the best value for the money out there."

A second study in the same issue of the journal found that only advanced colorectal cancers with the normal version of the KRAS gene will benefit from targeted drugs known as anti-epidermal growth factor receptor (anti-EGFR) antibodies, such as cetuximab (Erbitux) and panitumumab (Vectibix).

A review of previously conducted trials determined that people with advanced tumors with the mutated version of the gene did not live as long as those with the "wild-type" version of the gene.

SOURCES: David Weinberg, M.D., chairman, medicine, Fox Chase Cancer Center, Philadelphia; Vivek Kaul, M.D., associate professor, medicine, and acting chief, division of gastroenterology and hepatology, University of Rochester Medical Center, Strong Memorial Hospital, Rochester, N.Y.; Jan. 4, 2011, Annals of Internal Medicine
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Colonoscopies May Not Have 'Blind Spot' After All: MedlinePlus