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Colonoscopy use linked to decrease in colorectal cancer

Friday November 2, 2012
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Use of colonoscopy for colorectal cancer screening could explain a significant decrease in the cancer’s incidence over the past decade, according to a study.

Although colonoscopy is the most common colorectal cancer screening method, there has been conflicting evidence as to its effectiveness compared with sigmoidoscopy, researchers noted in background information for the study, which appears in the November issue of the journal Gastroenterology.

Researchers with the Stanford University School of Medicine scrutinized data collected from more than 2 million patients over the past 20 years, and found that a drop in colorectal cancer incidence correlated with Medicare’s extension of colonoscopy coverage in 2001.

"Widespread colonoscopy screening may actually be having an impact in the risk of colon cancer at the level of the general population," Uri Ladabaum, MD, MS, the study’s lead author and an associate professor of gastroenterology and hepatology at Stanford, said in a news release.

The researchers examined available data on the surgery rates for colorectal cancer and interpreted these in light of the dramatic rise in the use of colonoscopy that began more than a decade ago. They analyzed data from more than 2 million patients collected from the Nationwide Inpatient Sample, a large database that includes more than 1,000 hospitals.

Ladabaum and colleagues looked for trends in colorectal cancer surgery, which reflect cancer incidence. They also specifically looked for differences in rates of cancer in the lower versus the upper colon, noting that colonoscopy is hoped to have a benefit in preventing cancers in both areas due to its extended reach compared with sigmoidoscopy.

The study data suggest that increased use of colonoscopy may explain the decrease in incidence of upper colon cancer in the last decade. The overall rate for resecting colon cancer dropped from 71.1 to 47.3 per 100,000 people between 1993 and 2009. Resection rates for lower colorectal cancer decreased gradually (at a rate of about 1.2% per year) from 1993 to 1999, and then dropped more steeply (3.8% per year) from 1999 to 2009. In contrast, the resection rate for upper colon cancer remained steady until 2002, then started dropping at a rate of 3.1% per year until 2009.

These results support the idea that the drop in the incidence of lower colorectal cancer might be associated with screening in general, since some patients were already undergoing stool tests and sigmoidoscopy in the early 1990s, whereas the reduction in upper colon cancer incidence might be specifically associated with colonoscopy, Ladabaum said.

The study abstract is available at www.gastrojournal.org/article/S0016-5085%2812%2901132-8/abstract.


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