By Steven Reinberg
THURSDAY, May 21, 2015 (HealthDay News) -- A majority of people with a family history of colon cancer are not getting screened for the disease early enough, a new study finds.
Guidelines say colonoscopies should start at age 40 for people with a close relative who had colon cancer. However, only 38 percent of those people have a colonoscopy between ages 40 and 49, researchers report.
"This is an important finding, because people with a family history of colon cancer are at an increased risk for developing the disease early," said Dr. Richard Wender, chief cancer control officer at the American Cancer Society, who had no part in the study.
According to the society, as many as one in five people who develops colon cancer has other family members who had the disease. The risk is doubled for people with parents, siblings or children who had colon cancer. The risk is even higher if a relative was diagnosed with colon cancer when they were younger than 45, or if more than one relative had the disease.
The reasons for the increased risk are not always clear. Cancers can "run in families" because of genes, shared environmental factors, or both.
Screening is important because early detection of cancer improves the chances for effective treatment.
Wender said several factors may explain the low rate of screening among those most at risk, he said. For one, doctors and patients may not be aware of the guidelines.
Also, people need to track down their family's medical history, which may not be easy, Wender said. "It isn't good enough to say your aunt or father had cancer, you need the details -- what kind, when did it start, etcetera," he said.
Screening for colon cancer is recommended for everyone over 50. But those with a close relative who had colon cancer should begin screening at age 40, or 10 years before the youngest age at which a relative was diagnosed, Wender said.
He pointed out that a colonoscopy is the only recommended screening method for people with a family history of colon cancer. "We no longer recommend fecal blood testing, so the only option for those at above-average risk is colonoscopy," he said.
The report was published May 21 in the journal Preventing Chronic Disease.
Compared with people in their 50s, only about a third as many of those with a mother, father or sibling who had colon cancer had a colonoscopy between ages 40 and 49, study lead researcher Meng-Han Tsai, of the University of South Carolina, and colleagues found.
Having health insurance, however, was a major influence on whether someone had a colonoscopy, the researchers reported. People with insurance were three times more likely to have a colonoscopy than those without insurance.
The researchers said that although the rate of colonoscopies in the United States has increased five times since 2005, the number of younger people at risk for colon cancer who get a colonoscopy has lagged.
For the study, the researchers collected data on more than 26,000 men and women who took part in the 2005 and 2010 National Health Interview Survey. Among these people, almost 2,500 said they had a family history of colon cancer, but only 38 percent had a colonoscopy when they were 40 to 49, the researchers found.
Dr. Andrew Chan, an associate professor in the department of medicine at Harvard Medical School in Boston, said there has been an "alarming increase in the incidence of colon cancer in younger age groups."
Despite this, the study shows that rates of screening for individuals younger than 50 who have a family history of colon cancer are not optimal, Chan said. "The message that screening needs to start at a younger age for those with a family history may not be getting through to the general population," he said.
Wender said it isn't clear why the rates of colon cancer among younger people are increasing. It could be due to changes in diet and increases in overweight, obesity and inactivity, "all of which are risk factors for colon cancer," he said.