Colonoscopies could miss dangerous lesions: report

WASHINGTON (Reuters) - The most dangerous types of pre-cancerous lesions in the colon could be missed by colonoscopies, researchers cautioned on Wednesday.

More than 9 percent of the growths that could become tumors are flat and difficult to see, the team at the Veterans Affairs Palo Alto Health Care System in California found.

Colonoscopies are examinations of the colon that use an endoscope -- a little camera on a flexible tube. The doctor doing the examination can see and remove polyps, the small growths that can become tumors.

But not every pre-cancerous lesion stands up. There is a type called a flat, non-polypoid colorectal neoplasm and the California team found they are both more common and more dangerous than previously thought.

Dr. Roy Soetikno and colleagues examined the results of 1,819 colonoscopies among patients at their hospital.

They found 170 of these flat lesions, or 9.35 percent of all growths detected.

Once removed, they were 10 times as likely as the more obvious growths to contain cancerous tissue, Soetikno's team reported in the Journal of the American Medical Association.

They noted that up to 1 percent of patients who have colonoscopies develop cancer within three years afterward. These missed flat lesions may explain some of these cases, they said.

Dr. David Lieberman of the Portland VA Medical Center in Oregon agreed. "There has been increasing recognition that colonoscopy, even by experienced and well-trained endoscopists, may fail to detect important colon pathology," Lieberman wrote in a commentary.

And he noted that "virtual colonoscopies" done using computed tomography may miss these lesions.

Lieberman and Soetikno agreed that doctors doing colonoscopies need to keep a careful eye out for these flat lesions.

Colorectal cancer is the second leading cause of cancer death in the United States, with more than 150,000 cases and 52,000 deaths last year, according to the American Cancer Society.

Americans are told to get regular colonoscopies starting at age 50 -- younger if there is a family history of colon cancer.

(Reporting by Maggie Fox; Editing by Julie Steenhuysen and Eric Beech)