Retrospective colonoscopy study suggests women under 70 may be at very low risk for advanced proximal neoplasia

Screening some low-risk women for colorectal cancer using sigmoidoscopy rather than colonoscopy may be safe and effective, according to a new study.

Researchers used data from about 10,000 adults age 50 or older who consecutively underwent screening colonoscopy. Overall, they found that 77% had no neoplasia and 18% had one or more nonadvanced adenomas. Another 4.3% had advanced neoplasias (267 distally, 196 proximally, 30 both) and 0.33% had adenocarcinomas (18 distal, 15 proximal).

Results were published online by the American Journal of Medicine on Oct. 10.

Older patients and men were significantly more likely to have advanced proximal neoplasia. Women who were under 70 had only a 1.1% risk of advanced proximal neoplasia and if they had no distal neoplasia, that risk dropped to 0.86%. Study authors concluded that risk of advanced proximal neoplasia is a function of age and gender, and that women under 70 have a very low risk, especially if they have no distal adenoma.

Given this finding, sigmoidoscopy would be likely to provide a similar yield to colonoscopy for this patient population, the authors said. Therefore, it could be reasonable to tailor colonoscopy screening and consider using sigmoidoscopy more routinely for women under age 60 or 70. Adding sensitive fecal occult blood testing could potentially make this an even more effective strategy, as could identification of other risk factors to guide screening.

Use of sigmoidoscopy has declined in the U.S., and improvements in training and reimbursement might be required, given the benefits that this study and others have shown, the authors said.

However, they cautioned that the current study was limited by being extrapolated data from colonoscopies, rather than actual sigmoidoscopes. Nonspecialists might not always succeed in reaching the proximal descending colon with a sigmoidoscope, they noted. Future research should validate these findings and further assess the benefits, risks and costs of modifying screening practices.