New research led by the Memorial Sloan-Kettering Cancer Center in the US has for the first time found that removing precancerous polyps during colonoscopy may halve the risk of dying from the disease. The large team of endoscopists, radiologists, pathologists, and epidemiologists, write about their findings in the 23 February online issue of the New England Journal of Medicine, NEJM.

The study follows earlier research, also led by Memorial Sloan-Kettering, that showed removing precancerous polyps during colonoscopy prevents colorectal cancer from developing. Together, the two sets of findings would indicate that polyps removed during colonoscopy have the potential to progress and cause death from colorectal cancer.

Lead author Dr Ann G. Zauber, a biostatistician at Memorial Sloan-Kettering, said in a press statement:

“Our findings provide strong reassurance that there is a long-term benefit to removing these polyps and support continued recommendations of screening colonoscopy in people over age 50.”

A colonoscopy is a procedure where a doctor inserts 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 (polypectomy).

Adenomatous polyps are the most common abnormality seen during colonoscopy. Although not yet cancerous, they have the pontential to become cancerous if not removed.

Now this study indicates that if they are not removed, they grow into tumors that cause death.

For the study, Zauber and colleagues looked at data from patients taking part in the largest study of its kind, the NPS (short for National Polyp Study). The patients had been referred for initial colonoscopy between 1980 and 1990 at NPS centers throughout the US.

They included in the analysis 2,602 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.

They found that after a median of 15.8 years, 1,246 of the patients had died from any cause and 12 had died from colorectal cancer.

From data compiled by the Surveillance Epidemiology and End Results (SEER) 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 25.4.

So comparing the two rates, the researchers calculated the “standardized incidence-based mortality ratio was 0.47 (95% confidence interval [CI], 0.26 to 0.80) with colonoscopic polypectomy, suggesting a 53% reduction in mortality”.

Furthermore, they found that deaths from colorectal cancer was similar among patients with cancerous and those with non- cancerous polyps during the first ten years after having them removed.

Senior author Dr Sidney J. Winawer, a gastroenterologist at Memorial Sloan-Kettering and Principal Investigator of the NPS, said:

“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,” he added.

Winawer is an internationally recognized leader in the prevention of digestive cancers and is credited with introducing colonoscopy as a key component of national guidelines for colorectal cancer screening in the US and worldwide.

Estimates from the National Cancer Institute (NCI) suggest there were more than 100,000 new cases of colon cancer and nearly 40,000 of rectal cancer in 2011 in the US, and more than 49,000 people died from the two cancers combined during that year.

Funds from the NCI, The Society of Memorial Sloan-Kettering Cancer Center Fund, the Tavel-Reznik Fund, and the Cantor Colon Cancer Fund, helped pay for the study.

Written by Catharine Paddock PhD