TUESDAY, Oct. 23, 2012 (HealthDay News) -- The increased use of colonoscopy screening appears to be the reason for the significant decrease in colorectal cancer rates in the United States over the past decade, a new study indicates.
Stanford University School of Medicine researchers analyzed data collected from more than 2 million patients over the past 20 years. They found that a drop in colorectal cancer incidence correlated with Medicare's extension of colonoscopy coverage in 2001.
The overall rate for surgery to remove colorectal cancer dropped from 71 to 47 procedures per 100,000 people between 1993 and 2009.
"Widespread colonoscopy screening may actually be having an impact on the risk of colon cancer screening at the level of the general population," senior investigator Dr. Uri Ladabaum, an associate professor of gastroenterology and hepatology, said in a university news release.
The researchers also looked at differences in rates of cancer in the lower and upper colon to assess the benefit that colonoscopy screening is expected to have in preventing cancers in both locations.
The surgery rate for lower colorectal cancer decreased about by 1.2 percent per year between 1993 and 1999, and then dropped by 3.8 percent a year from 1999 to 2009. The surgery rate for upper colon cancer remained steady until 2002 and then began to drop at a rate of 3.1 percent per year until 2009.
These findings suggest that the decrease in lower colorectal cancer might be associated with general screening increases, since some patients were undergoing stool tests and sigmoidoscopy in the early 1990s, the researchers wrote. Sigmoidoscopy examines only a portion of the colon.
On the other hand, the drop in upper colorectal cancer rates might be specifically linked with increased colonoscopy screening, Ladabaum said.
The study, which found an association but not proof that increased screening led to lower cancer rates, was published online Oct. 23 in the journal Gastroenterology.
The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more about colonoscopy.