Lowering Your Risk of Colorectal Cancer

Advanced colorectal cancer diagnosis risks decreased by 70 percent with colonoscopies

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) March is Colorectal Cancer Awareness Month. Are you aware of the different types of screenings? And are you aware of which of these is the most effective?

Colonoscopy screenings may reduce the risk of being diagnosed with late-stage colorectal cancer by as much as 70 percent, according to a recent study.

The same study also found that this reduced risk applied to disease detected in both the right and left colon.

"Have your first colorectal screening at age 50."

The study was led by Chyke A. Doubeni, MD, MPH, Associate Professor of Family Medicine and Community Health at the Perelman School of Medicine at the University of Pennsylvania. 

The goal of the study was to document an association between screening colonoscopy and the risk for late-stage colorectal cancer (CRC) in adults with average risks for the disease.  

The researchers examined the health records of 1,012 average-risk adults between the ages of 55 and 85.

There are various ways to screen for colorectal cancer. Fecal occult blood tests (FOBT) involve collecting a bit of feces and sending it off to the lab. The test looks for blood in the stool.

A sigmoidoscopy is a procedure in which the lower (sigmoid) part of the colon is examined. For this test, a thin, lighted flexible tube is inserted into the rectum to look for polyps (precancerous growths), other abnormal growths, inflamed tissue, ulcers, bleeding and tumors. Polyps can be removed during this procedure.

A colonoscopy is like the sigmoidoscopy, except that it examines the entire colon – from the rectum all the way through the large intestine.

By the way, your colon probably measures about 25 feet long!

The colon is shaped like an upside-down letter “u”. A colonoscopy looks at both the right (ascending colon) and left (descending colon) sides of the colon, as well as the part that goes across the abdomen (transverse colon). 

For this study, 474 patients who had been diagnosed with advanced CRC were compared with 538 healthy controls.

Individuals who had been screened with colonoscopy had a significant – 70 percent - overall lower risk for advanced colorectal cancer diagnosis in both the right and left sides of the colon.

Researchers also looked at the effectiveness of sigmoidoscopy. This procedure was as effective as colonoscopy in picking up left-sided cancers. Sigmoidoscopy did not significantly decrease the risks of right-sided colon cancers.

“Colonoscopy is the gold standard for colorectal cancer screening, and its status as such is re-enforced by this study,” David A. August, MD, professor of surgery and chief of surgery at The Cancer Institute of New Jersey, told dailyRx News.

“The 70 percent reduction observed in late stage colorectal cancers is likely attributable to both detection of precancerous adenomatous polyps (thereby facilitating prevention of invasive cancer development) and to the detection of more curable early stage cancers,” Dr. August said.

“The observation that screening sigmoidoscopy has a similar effect, but only for left sided cancers is both clinically and mechanistically important. It emphasizes the need for screening that visualizes the entire colon. It also confirms that the benefit from colonoscopy is attributable to the actual visualization of lesions, and not to some other associated but unrelated factors,” Dr. August explained.

The authors noted that this was an observational study and, as such, cannot establish cause and effect.

This study was published March 4 in the Annals of Internal Medicine. This research was supported by the National Cancer Institute of the National Institutes of Health.

Reviewed by: 
Review Date: 
March 4, 2013
Last Updated:
August 15, 2013