Initial Colonoscopy Key to Cancer Detection

TUESDAY, Oct. 16 (HealthDay News) -- A first-time colonoscopy to remove precancerous polyps plays a bigger role in reducing the risk of dying from colon cancer than do follow-up screenings done years later, a new study suggests.

Researchers found that patients who forego follow-up colonoscopies in the decade following the initial procedure will still reap the benefits sown by a first removal of polyps -- called a polypectomy.

Post-polypectomy colonoscopies do, however, become more important in protecting against colon cancer death as patients enter their second decade following the first colonoscopy, the study authors said.

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"The initial colonoscopy has a major impact -- a huge, huge effect -- on reducing colon cancer deaths," said study lead author Ann G. Zauber, an associate attending biostatistician at Memorial Sloan-Kettering Cancer Center's department of epidemiology and biostatistics, in New York City.

"The risk for dying from colon cancer drops 90 percent after the initial colonoscopy," she said. "And in the first 10 years, 90 percent of that reduction is due to that first procedure. Only 10 percent of the risk drop is due to follow-up colonoscopies."

Zauber presented her findings Monday at the American College of Gastroenterology annual meeting, in Philadelphia.

Her team's conclusions were derived from a review of data on colon cancer incidence and deaths that had been collected by the National Polyp Study. The study had tracked the development of polyps and invasive colorectal cancer following a first-time colonoscopy.

For the new study, Zauber and her colleagues fed the National Polyp Study data into a computer model that projected colon cancer incidence and deaths 30 years down the road. The review included three different types of patients -- those who had no preventive screening of any kind; those who underwent only an initial colonoscopy and polypectomy; and those who had both a colonoscopy/polypectomy and follow-up screenings.

The Sloan-Kettering researchers noted that prior research had indicated that a combination of initial polypectomy and follow-up screenings reduced the incidence of colon cancer by between 76 percent and 90 percent. Previous work had also shown that this dual preventative approach reduced the rate of colorectal cancer deaths by between 69 percent and 92 percent.