Oct. 15, 2007 (Philadelphia) -- An initial colonoscopy during which the colon is cleared of precancerous polyps significantly reduces deaths from colon cancer -- even if there are no follow-up exams, researchers report.
In a 20-year study of more than 2,500 people, the risk of dying from colon cancer was about 90% lower if people underwent both the initial and follow-up procedures than if they underwent neither.
But over the first 10 years, 90% of that effect was due to the initial exam, says Ann G. Zauber, PhD, a biostatistician at Memorial Sloan-Kettering Cancer Center in New York.
Over the next 10 years, 55% of the effect was still due to the initial procedure.
“Removing [potentially precancerous growths] has a huge effect on reducing colon cancer mortality,” Zauber tells WebMD.
“The surveillance colonoscopies had more of an effect in the second decade than in the first, but the initial procedure still is the major effect,” she says.
The findings were presented at the annual meeting of the American College of Gastroenterology (ACG).
Colonoscopy Plus Polyp Removal Cuts Colon Cancer Deaths
The researchers analyzed data on 2,602 men and women in the National Polyp Study, the landmark trial that showed that an initial colonoscopy during which the colon is cleared of precancerous polyps with regular follow-up exams significantly cut the risk of developing colon cancer by up 90% and of dying from the cancer by up to 92%.
Using sophisticated mathematical modeling, they found that:
- Failing to do a colonoscopy and remove precancerous polyps is associated with a 5.5% risk of death over 20 years.
- Doing only an initial exam with removal of precancerous polyps is associated with a 2.5% risk of death over 20 years.
- Doing both an initial exam to remove precancerous polyps and follow-up exams is associated with less than a 1% risk of death over 20 years.
ACG President David A. Johnson, MD, a gastroenterologist at Eastern Virginia Medical School in Norfolk, tells WebMD that the findings could influence guidelines, lengthening the time between exams for people who have had polyps removed to six years or more. Recommendations now call for a follow-up colonoscopy in three to five years.
“Once you clear the colon, maybe you can wait a longer time depending on risk. That first removal of polyps is the time when you make the biggest impact on risk for colon cancer incidence and colon cancer death,” Johnson says.