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 research hasn’t shown before 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 needed to get ready for it.
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 today’s New England Journal of Medicine.
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 day before to clear out the bowel. It usually costs more than $1,000, compared with a $20 stool test.
Researchers at Sloan-Kettering previously showed that removing polyps during colonoscopy can prevent colon cancer from developing, but it was not clear whether it saved lives.
The new study followed 2,602 patients who had precancerous growths removed during colonoscopies 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 randomized 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 Smith, who had no role in the research.