A colonoscopy is a procedure involving the insertion of a tube enclosing a video camera into the patient’s rectum and slides it up into the colon. A skilled gastroenterologist can see with the camera whether there are any suspicious-looking tumor-like growths or “adenomatous polyps” and safely remove them. Adenomatous polyps are the most common abnormality discovered during colonoscopy. Although they are not cancerous, they have the potential to become cancerous if they are not removed. This study now indicates that if they are not removed, they can grow into tumors that cause death.
For the study, lead author Dr. Ann Auber and colleagues examined data from patients participating in the largest study of its kind, the National Polyp Study. The analysis included 2,600 patients who had precancerous polyps removed during colonoscopy. For a maximum follow-up time of 23 years, the researchers looked up the cause of any deaths in the group using the National Death Index.
The researchers found that after a median of 15.8 years, over 1,200 of the patients had died from any cause and 12 had died from colorectal cancer. From data taken from the Surveillance Epidemiology and End Results Program, the rate of death from colorectal cancer in the general population for a similar group of this size, age, and gender mix, would have been 25.
So in comparing the two rates, the researchers calculated the standardized incidence-based mortality ratio and found a 53% reduction in mortality. Furthermore, they found that deaths from colorectal cancer were similar among patients with cancerous and those with non-cancerous polyps during the first ten years after having them removed.
Senior author, Dr. Sidney Winawer, concludes, "The magnitude of reduction in mortality seen after this procedure is likely due to high-quality colonoscopy performed by well- trained, experienced gastroenterologists. Randomized controlled trials of screening colonoscopy in the general population underway in the US and Europe will in 10 to 15 years provide further evidence for this potentially powerful cancer prevention approach.”