(Reuters Health) - Doctors now have strong evidence that colonoscopies save lives, a finding that may encourage more people to get the dreaded tests to detect and prevent colon cancer.
A team at Memorial Sloan-Kettering Cancer Center in New York found that colonoscopies in which precancerous polyps, known as adenomas, are removed can cut the risk of dying from colon cancer by 53 percent. The study appears in the New England Journal of Medicine.
In theory, adenoma removal saves lives by preventing a tumor. Ann Zauber of the Memorial Sloan-Kettering Cancer Center in New York, chief author of the long-term evaluation of polyp removal, and her colleagues said their work demonstrates that.
"This study is showing both a reduction in colon cancer incidence and colon cancer deaths by removing the adenomas, and it's a long-term effect" she said in a telephone interview. "This is reassuring for people to come in for screening."
One in 20 Americans will develop colorectal cancer. About 140,000 cases are diagnosed in the United States each year, resulting in about 49,000 deaths, according to the National Cancer Institute. It is the third most common cancer worldwide.
Confirmation that colonoscopies save lives comes as researchers consider the value of popular screening tests, such as those for prostate cancer. At issue is whether such screening tests actually save lives or merely lead to diagnoses of more tumors that may pose little danger to a patient and trigger unnecessary treatment.
In standard colonoscopies, a tiny camera is threaded up through the rectum. The device has a little pair of clippers on the end to remove suspicious-looking growths so they can be tested to see if they might become cancerous.
Only about half of people recommended for colonoscopies get them, in part because the procedure is embarrassing, uncomfortable and can, in rare cases, cause injury.
The study's conclusion is based on people who were sent for a colonoscopy between 1980 and 1990. The Zauber team compared the death rate in their study to the estimated death rate from a national cancer tracking effort known as the Surveillance Epidemiology and End Results (SEER) program.
Over a period as long as 23 years, the rate from colorectal cancer among the 2,602 people who originally had adenomas removed was 53 percent lower than would be expected based on the rates seen in the government study. In all, 12 died from cancer in the removal group, while 25 had normally been expected to die of colorectal disease.
The lower rate includes the fact that 81 percent of the patients who had polyps removed continued to have periodic colonoscopies to check for growths.
STOOL SAMPLE TEST
Meanwhile, a separate study in the journal by a team in Spain suggests that a relatively inexpensive and non-invasive test that looks at stool samples is also highly effective at finding polyps, but has yet to show if it saves lives.
Taken together, the findings suggest the two methods could be used to identify more cases of colon cancer.
"An appealing concept would be to use colonoscopy as a triage screening test, offering it once for everybody at 60 years of age" and using it to classify people into high- and low-risk categories, Dr. Michael Bretthauer of Oslo University Hospital and Dr. Mette Kalager of Telemark Hospital, both in Norway, wrote in an editorial in the journal.
Low-risk people would not need further screening while those with adenomas would be evaluated regularly.
The U.S. Preventive Services Task Force, a government-backed agency, recommends screening for people age 50 to 75 years by one of three methods: a colonoscopy every 10 years; annual stool testing; or a less-thorough look into the colon (known as flexible sigmoidoscopy) every five years in conjunction with stool testing every two to three years.
The COLONPREV study, being conducted in Spain, is designed to compare 10-year death rates in two groups: volunteers who received a one-time colonoscopy and volunteers who are being screened every two years using fecal immunochemical testing (FIT), a form of blood stool testing. A positive FIT test led to a colonoscopy.
After the first round of testing, the researchers said, colorectal cancer was found in 30 people in the 26,703-member colonoscopy group and 33 in the 26,599-person FIT group.
But colonoscopy uncovered twice as many advanced adenomas, about 2 percent of the sample versus 1 percent.
The chief author of the Spanish study, Enrique Quintero of Hospital Universitario de Canarias, said it was encouraging that the cheaper fecal test "detected half the advanced adenomas just in the first round."
The next round of FIT tests will uncover more growths, he predicted. Death rates will not be examined until the 10-year follow-up is completed in 2021.
Quintero and his team also found that the people assigned to the FIT group were more likely to participate in screening than those who were in line for a colonoscopy.
(Additional reporting by Julie Steenhuysen in Chicago; Editing by Michele Gershberg and Vicki Allen)