LOS ANGELES — Millions of people have endured a colonoscopy, believing the dreaded exam may help keep them from dying of colon cancer. For the first time, a major study offers clear evidence that it does.
Removing precancerous growths spotted during the test can cut the risk of dying from colon cancer in half, the study suggests. Doctors have long assumed a benefit, but until now research hasn’t shown that removing polyps would improve survival - the key measure of any cancer screening’s worth.
Some people skip the test because of the unpleasant steps need to get ready for it.
“Sure, it’s a pain in the neck. People complain to me all the time, ‘It’s horrible. It’s terrible,’ ” said Dr. Sidney Winawer, a gastroenterologist at Memorial Sloan-Kettering Cancer Center in New York who helped lead the study. “But look at the alternative.”
A second study in Europe found that colonoscopies did a better job of finding polyps than another common screening tool - tests that look for blood in stool. Both studies were published in Thursday’s New England Journal of Medicine.
Colorectal cancer is the second-leading cause of cancer death in the U.S. and the fourth worldwide. More than 143,000 new cases of cancers of the colon or rectum are expected in the U.S. this year and nearly 52,000 people will die from it, according to the American Cancer Society.
People of average risk of colon cancer ages 50 to 75 should get screened, but only about half in the U.S. do. A government-appointed panel of experts recommends one of three methods: annual stool blood tests; a sigmoidoscopy (scope exam of the lower bowel) every five years, plus stool tests every three years; or a colonoscopy once a decade.
In a colonoscopy, a thin, flexible tube with a tiny camera is guided through the large intestine. Growths can be snipped off and checked for cancer. Patients are sedated, but many dread the test because it requires patients to eat a modified diet and drink solutions the previous day to clear the bowels. It usually costs more than $1,000, compared with a $20 stool test.
The new study involved 2,602 patients who had precancerous growths removed during colonoscopies and who were followed for an average of 15 years. Their risk of dying from colon cancer was 53 percent lower than what would be expected among a similar group in the general population - 12 patients followed in the study died, versus 25 estimated deaths in the general population.
The study was not a random trial that’s the gold standard in medical research. But Robert Smith, director of screening at the American Cancer Society, said it’s the first direct evidence that removing polyps can reduce the risk of colon cancer death.
“There’s no question that these are findings that we can take to the bank,” said Mr. Smith, who had no role in the research.
In the second study in the journal, led by researchers in Spain, about 53,000 participants underwent a colonoscopy or a stool blood test. Both tests found similar numbers of colon cancer cases - about 30 in each group. But colonoscopies found advanced growths in twice as many people - 514 versus 231 of those given the stool test and 10 times more people with less-serious growths than did the stool tests.
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