Currently, people at averageare told to start screening for the disease at age 50. But a new study raises the question of whether earlier screening could be better.
Looking at more than 6,000 patients who underwent colonoscopies, French researchers found the rate of abnormal colon growths started to rise sharply at age 45.
Among 45- to 49-year-old patients, 26 percent showed growths called adenomas -- a type of polyp that could eventually become cancerous. That compared with 13 percent of patients ages 40 to 44.
In addition, so-called "neoplastic" growths were found in nearly 4 percent of patients ages 45 to 49 -- versus only 0.8 percent of people in their early 40s. A neoplasm refers to a new, uncontrolled growth of abnormal tissue, which can be cancerous or not.
According to lead researcher Dr. David Karsenti, the preliminary findings argue for earlier colon cancer screening -- starting at age 45, rather than 50.
Karsenti is a gastroenterologist with Clinique de Bercy in Charenton-le-Pont, France. He was scheduled to present the findings Monday at the United European Gastroenterology meeting, in Barcelona, Spain.
He said that based on the neoplasm rate among 45- to 49-year-olds, delaying screening to age 50 could potentially dim some patients' chances of.
However, an expert with the American Cancer Society said no conclusions can be drawn from the findings.
Dr. Otis Brawley, chief medical officer for the cancer society, pointed to a "major problem" with the study: All of the patients were referred to a gastroenterologist for a colonoscopy, presumably because they had symptoms.
In contrast, colon cancer screening, by definition, is done when people are symptom-free. The point is to catch cancer early or, better yet, abnormal growths that can be removed before they have a chance to become cancerous.
"These findings aren't going to change what we recommend as far as screening average-risk people," Brawley said.
The cancer society and other medical groups suggest people at average risk of colon cancer begin screening for the disease at age 50. That can be done in a number of ways -- including a colonoscopy every 10 years, or yearly stool tests.
That recommendation, Brawley said, is based on strong evidence that screening from age 50 onward cuts the risk of dying from colon cancer. That evidence includes findings from several clinical trials, which are considered the "gold standard" in medicine, he said.
There is no similar support for routinely screening younger people, Brawley said.
However, he stressed, earlier screening is advised for those at higher-than-average risk of colon cancer. That includes people with a strong family history of colon cancer.
According to the cancer society, a "strong" family history means having a first-degree blood relative who was diagnosed with colon cancer or adenomas before age 60 -- or two first-degree relatives diagnosed at any age. A first-degree relative is a parent, sibling or child.
Those people, the guidelines say, should start screening either at age 40, or 10 years before the earliest diagnosis in the family.
So it's important, Brawley said, that people find out their family history in order to know whether they are at average or higher risk.
Why not just screen younger people, even if it hasn't been proven to prevent colon cancer deaths?
With any screening tests, there are risks, Brawley said. Less-invasive tests can give "false-positive" results that lead to needless invasive tests, and invasive tests carry a higher risk of harm.
Colonoscopies have a small risk of bleeding, bowel tears and infections, the cancer society notes. Then there's the expense and the unpleasant bowel preparation before the procedure.
So before subjecting healthy people to screening tests, Brawley explained, it's important to know that it's worth it.
That said, younger people do sometimes develop colon cancer even if they are not known to be higher-risk. Brawley said more research is needed to understand why, and whether different screening approaches would be beneficial.
"We need more solid, well-designed studies to look at colon cancer in younger people," he said.
On average, Americans have between a 4 and 5 percent lifetime chance of developing colon cancer, the cancer society says. When the disease is caught early, the five-year survival rate is around 90 percent.
Research presented at meetings is usually considered preliminary until published in a peer-reviewed medical journal.