Major study showed that the screening cut death rate from colorectal cancer by 53 percent.
Millions of people have endured a colonoscopy, believing that the dreaded exam -- perhaps the most unloved cancer screening test -- may help keep them from dying of colon cancer. For the first time, a major study offers clear evidence that it does.
Although many people have assumed the colonoscopy must save lives because it is so often recommended, strong evidence has been lacking -- until now. In patients tracked for as long as 20 years, the death rate from colorectal cancer was cut by 53 percent in those who had the test and whose doctors removed precancerous growths, known as adenomatous polyps, researchers reported Wednesday in the New England Journal of Medicine. The test examines the inside of the intestine with a camera-tipped tube.
"For any cancer screening test, reduction of cancer-related mortality is the holy grail," said Dr. Gina Vaccaro, a gastrointestinal oncologist at the Knight Cancer Institute at Oregon Health and Science University who was not involved in the research. "This study does show that mortality is reduced if polyps are removed, and 53 percent is a very robust reduction."
Colorectal tumors are a major cause of U.S. cancer death and one of the few cancers that can be prevented with screening. This year, more than 143,000 new cases and 51,000 deaths are expected. Incidence and death rates have been declining for about 20 years, probably because of increased screening and better treatments. People ages 50 to 75 should get screened, but only about 6 in 10 adults are up to date on getting screened, federal estimates said.
The new study on colonoscopy has limitations -- it is not a randomized clinical trial -- but some experts say it nonetheless was well-done and probes the effectiveness of the procedure.
Earlier research had proved that removing precancerous polyps could greatly reduce the incidence of colorectal cancer. But a major question remained: Did removing the polyps really save lives? In theory, it was possible that doctors were finding growths that would not have killed the patient, or missing ones that could be fatal.
"This study puts that argument to rest," said Dr. David Rothenberger, a professor and deputy chairman of surgery at the University of Minnesota Masonic Cancer Center. He was not part of the study.
Robert A. Smith, the senior director for cancer control at the American Cancer Society, said, "This is a very big deal."
A team of researchers led by Dr. Sidney Winawer, a gastroenterologist at Memorial Sloan-Kettering Cancer Center in New York City, followed 2,602 patients who had adenomatous polyps removed during colonoscopies from 1980 to 1990. Doctors compared their death rate from colorectal cancer with that of the general population, where 25.4 deaths from the disease would have been expected in a group the same size. But among the polyp group, there were only 12 deaths from colorectal cancer, which translates into a 53 percent reduction in the death rate.
And a second study led by researchers in Spain, also published in the New England Journal of Medicine, found that colonoscopies did a better job of finding polyps than another common screening tool -- tests that look for blood in stool. In that test, about 53,000 participants were given a colonoscopy or a stool blood test. Both tests found similar numbers of colon cancer cases -- about 30 in each group. However, colonoscopies found advanced growths in twice as many people -- 514 versus 231 of those given the stool test. Colonoscopies also found 10 times more people with less serious growths than the stool test did.
In a colonoscopy, a thin tube with a tiny camera is guided through the large intestine. Growths can be snipped 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.
A colonoscopy does not have to be done every year: If there are no polyps, it is recommended just once every 10 years. People with polyps are usually told to have the test every three years.
But Dr. Harold Sox, an emeritus professor of medicine at Dartmouth Medical School and former editor of a leading medical journal, Annals of Internal Medicine, cautioned that the new study was not the last word. He said it was not clear that the same reduction in the death rate found in the study would occur in the general population. Nonetheless, he said, "I suspect that removing polyps does reduce colorectal cancer mortality."
"Any screening is better than none," Winawer said. "The best test is the one that gets done, and that gets done well."
The AP contributed to this report.