A Canadian study, published in the Annals of Internal Medicine, concluded that colonoscopies may detect polyps and early cancers only 60 to 70 percent of the times, even if they have long been considered the gold standard for colorectal cancer screening. Previous studies have shown that a colonoscopy is 90 percent effective in detecting the second leading cancer killer of men and women in the U.S.

 

“When you compare colonoscopy to something like mammography, this is a much better test, but it's not perfect,” said Dr. Nancy Baxter, the study’s lead author and a colorectal surgeon at St. Michael’s Hospital in Toronto.

 

One possible explanation for this finding could be the fact that some colonoscopies that are considered “complete” might not evaluate the entire right colon, Baxter said. Alternatively, it could be that bowel preparation isn’t as good in the right colon, making it more difficult for doctors to spot pre-cancerous polyps, or polyps in the right colon might be flatter and thus more difficult to see and remove during the test.

 

Although the new study shows a decline in the efficiency of a colonoscopy, it still worth having it once you’re over 50. Statistics show that colorectal cancer incidence is 14 times higher in adults 50 and older than in people under 50. Also people with a history of colorectal cancer in their family should be the first to be screened.

 

When deciding to have this test, people should take great care in selecting their doctors to do their colonoscopies and make sure they follow their doctors' directions to the letter when preparing for the procedure.

 

The American Cancer Society estimates that 148,810 people will be diagnosed with colorectal cancer this year and 49,960 people will die of the disease.