A common test can cut the risk of dying from colorectal cancer by as much as a third over three decades, a new study shows.
Researchers examining cancer screening records for more than 45,000 people ages 50 to 80 found those receiving an annual fecal occult-blood test had a 32 percent lower risk of death from colon cancer over a 30 year follow-up period compared to those who went unscreened. People screened every two years lowered their colon cancer death risk by 22 percent.
The findings from the Minnesota Colon Cancer Control Study support previous research showing a similar reduction in colon cancer mortality up to 20 years following the fecal occult-blood test.
The new results were surprising and remarkable, said Dr. Aasma Shaukat, a gastroenterologist with the Minneapolis V.A. Medical Center and the University of Minnesota and the study's chief author.
"We weren't expecting such a sustained, long-term benefit in colon cancer mortality reduction with stool cards," she said.
The fecal occult-blood test, also referred to as a stool card, is a common colon cancer screening tool that detects the presence of blood in stool. Patients who have a positive test result are typically referred for colonoscopies to determine if they have colon cancer.
The new, long-term mortality findings come from an analysis of research in two phases from 1976 through 1992. That randomized trial enrolled 46,551 participants. About a third were screened yearly for colon cancer, another third were screened every two years, and the final third received no screening. Researchers obtained updated cause of death information for study participants from the National Death Index.
The data show "aggressive screening, versus less screening, might be of benefit," Shaukat said.
Current screening guidelines in the U.S. recommend a variety of colon cancer screening options that begin at age 50 for most people.
The study findings support those guidelines, though there were differences in fecal occult-blood testing benefits, depending on gender, Shaukat said. The study found that the test benefits men more than women in the early years of screening, prior to age 60. In women, the mortality benefit was seen largely at age 60 and above.
"At least our data suggest that women 50 to 60 don't derive the same benefit," said Shaukat. "And if screening is started in women at age 60, the long-term benefit is identical, (compared to) if it was started at age 50."
Women lag behind men by about 10 years in their risk of developing colon cancer and also dying from it, Shaukat said. The protective effect of estrogen is thought to be a contributing factor to the difference, along with healthier diet and lifestyle factors for women, she added.
The study did not compare the effectiveness of fecal occult-blood tests with colonoscopies, which is the predominant colon cancer screening tool in the U.S. Shaukat said she and her V.A. colleagues around the country are currently collaborating on a study that directly compares stool cards to colonoscopy. Those results are expected in about seven to eight years.
Until then, the research shows that fecal occult-blood tests are a viable screening tool, if used regularly, she added.
Shaukat said she's noticed that it is easier to convince some patients to take the stool test, than it is to convince them to get a colonoscopy.
"At the moment I think the best test is the one that gets done," said Shaukat. "It has a lot of advantages in being inexpensive, readily available and carries no harms. So this might be a very good option for individuals to undergo. And if it's positive they would get a colonoscopy. But if it's negative they could get stool cards every year."
The study, published in the New England Journal of Medicine , does not reveal why the risk of death from colon cancer would be lower decades after screening ended. But Shaukat said it would be common practice to remove pre-cancerous polyps at the time of colonoscopy for individuals who had positive test results.
Intervention, she added, would likely "result in a long-term benefit" by helping some people avoid ever developing colon cancer.