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 m
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