TUESDAY, March 4, 2008 (HealthDay News) -- While the majority of colon cancers were thought to develop from polyps, a new study challenges that assumption and points out that so-called non-polypoid (flat or depressed) lesions in the colon are also likely to turn into cancer.
A study in the March 5 issue of the Journal of the American Medical Association reports that such lesions were present in almost 10 percent of people screened for the study, and that these lesions were 10 times more likely to be cancerous than polyps were.
"Colorectal cancer is common, it is preventable, and it can be prevented even better," said the study's lead author, Dr. Roy Soetikno, chief of gastroenterology at the Veterans Affairs Palo Alto Health Care System in California. "Not all colon cancers are created equal, and doctors will now start looking for those that aren't so obvious."
Soetikno said it's like when you cross the street: You look left, and you look right before you cross, but "you never look carefully for the pothole on the street. This study is saying that doctors need to look at everything, including the potholes, to do a much better job."
The good news is that with current colonoscopy technology, doctors can find and remove these lesions. The bad news is that virtual colonoscopy (CT colonography) is not yet sensitive enough to pick up these dangerous lesions.
Previously, experts believed that these non-polypoid lesions were mainly found in people of Japanese descent, and U.S. doctors weren't specially trained to look for them. Soetikno and his colleagues underwent special training with specialists from Japanese endoscopy centers to learn to better detect these potentially pre-cancerous lesions.
Using their new knowledge, the U.S. researchers searched for non-polypoid lesions among 1,819 veterans who were already scheduled to undergo standard colonoscopy. The average age of the study participants was 64, and 95 percent were male. And, most -- 79 percent -- were white.
The researchers found that 764 people (42 percent) had at least one unusual colorectal growth. One hundred and seventy (9.35 percent) had non-polypoid colorectal lesions. Eighty-one of these people had both polyps and non-polypoid lesions.
Soetikno said that in a general screening, the chance of finding a polyp is about 30 percent, and that doctors are about five times more likely to find polyps than non-polypoid lesions. But, non-polypoid lesions are far more likely to be cancerous than polyps are. The new study found the odds were 9.78 times higher that a non-polypoid lesion would be cancerous than a polyp.
Generally, non-polypoid lesions can be removed at the time of a colonoscopy. If the center where you have your colonscopy done doesn't have the expertise yet, you may have to undergo a second procedure to have the lesion removed. Also, Soetikno said that if the lesion is completely flat, you'll probably need to go to a more experienced center to have it removed.
Dr. David Lieberman is chief of the division of gastroenterology at Oregon Health and Science University and the Portland VA Medical Center, and author of an accompanying editorial in the journal. He said, "I think this study will be very enlightening for the [gastroenterology] community. It points out that the non-polypoid lesions are found in the U.S., and that they can be somewhat ominous because they carry a reasonably high risk of cancer."
Both Soetikno and Lieberman stressed that this study's findings don't mean that a colonoscopy isn't useful. It definitely is, at both screening for and preventing colorectal cancer, the second leading cause of cancer death in the United States.
"Colonoscopy is a very good tool. It's not perfect, but it's a good tool," Lieberman said. "This study emphasizes the need for a high-quality examination with a fully-trained endoscopic technician," he added.
To learn more about colonoscopy, visit the American Gastroenterological Association.