Sigmoidoscopy found to reduce colorectal cancer rates


  • Carrie Printz

In a nearly 20-year study sponsored by the National Cancer Institute, researchers found that flexible sigmoidoscopy is effective in reducing rates of new colorectal cancer cases and deaths.

The study, published in the New England Journal of Medicine, found that overall colorectal cancer deaths were reduced by 26% and overall new cases were reduced by 21% as a result of screening with sigmoidoscopy.1

In sigmoidoscopy, the lower colon is examined by a thin, flexible, tube-like instrument (the sigmoidoscope) to view the anus, rectum, and sigmoid colon. Not only does this method have fewer side effects than colonoscopy, it also requires less bowel preparation and is less likely to cause bowel perforation. Colonoscopy uses a similarly flexible but longer tube to view the entire colon.

Both screening methods are more sensitive than fecal occult blood testing for detecting polyps that can lead to colorectal cancer. Precancerous polyps can be removed during either procedure. The main message is that all individuals aged 50 years and older should be screened for the disease, says Christine Berg, MD, chief of the National Cancer Institue's Early Detection Research Group and project officer of the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial.

As part of the PLCO trial, a total of 14,900 men and women aged 55 years to 74 years were randomly assigned to receive flexible sigmoidoscopy screening or usual care during the period between 1993 and 2001. In addition to comparing overall colorectal cancer incidence and mortality in the 2 groups, researchers also compared incidence and mortality according to the location of the cancers that developed: either “distal” or “proximal.”

Findings indicated that over the course of 10 years, if 1000 people followed the PLCO protocol of 2 sigmoidoscopy screenings, there would be approximately 3 fewer new cases and 1 less death from colorectal cancer than in a comparable group not being screened. The incidence and mortality of distal colorectal cancer were reduced by 29% and 50%, respectively, in the screening group. Although there was no statistically significant decline in deaths from proximal colorectal cancer, the incidence was reduced by 14% in the screening group.