Colonoscopy vs Sigmoidoscopy in Asymptomatic Women

SAN DIEGO—In the VA Cooperative Study 380, screening colonoscopy found advanced adenomas in approximately 10% of asymptomatic veterans, and approximately 20% to 40% of those patients had no lesions within reach of a sigmoidoscope, depending on the insertion depth of the scope.

However, 97% of the study population were men, and that left researchers without adequate data about the efficacy of screening colonoscopy in women.

“We decided to duplicate the VA 380 study, but this time with women only,” said Brooks Cash, MD, a gastroenterology fellow at the National Naval Medical Center, Bethesda. He presented the results at an American Gastroenterological Association research forum held during the Digestive Disease Week conference.

Subjects completed questionnaires about multiple risk factors for adenomas prior to undergoing colonoscopy. The questions dealt with age, race, alcohol use, tobacco use, NSAID use, and family history of colon cancer.

The study included consecutive asymptomatic women referred for screening. Excluded were women who had had colonoscopy or barium enema within the last 10 years, flexible sigmoidoscopy in the last 5 years, hematochezia within the last year, iron deficiency anemia, or positive stool guiaics.

Dr. Cash said that the sample size calculations mirror that of the VA Cooperative Study 380, with 215 completing the study thus far of a planned 1,500. The mean age of these initial patients was 58.7 years; 15.8% had a positive family history, and 7.9% were black.

Of the 215 women screened, 40 women (18.6%) were found to have adenomas during colonoscopy. Ten (4.65%) had advanced adenomas. Of these 10, four had no adenomas within reach of the flexible sigmoidoscopy.

“Had flexible sigmoidoscopy been the only screening test, those proximal adenomas would have been missed,” Dr. Cash said. “Based on our preliminary data, I think colonoscopy may be preferable to flexible sigmoidoscopy for colorectal cancer screening in asymptomatic women.”

Age over 65 was the only significant risk factor for colorectal cancer in this group, although alcohol use (more than 2 oz daily) approached significance as an independent risk factor.