Colonoscopy cuts cancer risk: study

Colorectal death rate reduced 53 per cent when polyps removed during controversial screening process

Doctors have proved for the first time that removing polyps during a screening colonoscopy prevents colorectal cancer from developing and thus prevents deaths from the disease, according to an analysis published Thursday.

By studying the fate of 2,602 highrisk patients over 23 years, a team of medical investigators led by researchers at Memorial Sloan- Kettering Cancer Center in Manhattan concluded colonoscopy cuts the risk of colorectal cancer death in half.

“The evidence demonstrates a striking reduction in death,” said Dr. Sidney J. Winawer, lead investigator of the National Polyp Study and a SloanKettering gastroenterologist.

“By finding and removing polyps, there was a 53 per cent reduction in the death rate,” Winawer said, adding colorectal cancer is the only malignancy that can be prevented through a screening technique.

For years, doctors knew colonoscopy helped reduce the risk of colorectal cancer when precancerous growths — polyps — were removed. But no one had ever quantified by how much colonoscopy reduced the risk of death.

Knowing that figure, doctors said, would help bolster another observation: Cancer statistics were revealing a noticeable decline in colorectal cancer incidence over the past two decades. Doctors believed — but had no proof — that the decrease could be attributed to colonoscopies.

Dr. Ann Zauber, senior author of the study, which is reported in Thursday’s New England Journal of Medicine, said she and her team proved colonoscopy cut the death rate in half by comparing colorectal cancer deaths of study participants to those of people in the general population.

In the group of 2,602 patients, 25.4 deaths from the disease would have been expected. Instead, there were only 12.

Despite advances in screening, colorectal cancer remains a potent cause of cancer mortality, yet only 30 per cent of people 50 and older undergo the test in the U. S., according to data from the National Cancer Institute.

The institute also estimates more than 140,000 new cases will be diagnosed this year and that more than 50,000 people will die of the disease.

Yet, even in the face of colonoscopy’s benefits, it has come under fire, Winawer said.

“The effectiveness of colonoscopy has been challenged recently, along with mammography, the PSA and CT scanning for lung cancer,” Winawer said.

“So, yes, these questions have been raised, but you can’t ignore the major benefits from this form of screening.”

Two years ago, Dr. Alfred Neugut and Dr. Benjamin Lebwohl of Columbia University argued colonoscopy was no more effective than sigmoidoscopy, another screening technique.

Last year, relying on New York State Health Department data, Dr. David Bernstein, chief of gastroenterology at North Shore University Hospital in Manhasset, reported on a colonoscopy risk factor: possible colon perforations during the procedure.

Bernstein said while perforations are rare, colonoscopy is best performed by skilled specialists.

Zauber, meanwhile, noted the new results should inspire renewed confidence in the procedure.

“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.”