INDIANAPOLIS — While the incidence of colon cancer has been declining in individuals 50 years old and older in the United States, it is steadily rising in those under age 50. With funding from the U.S. Department of Veterans Affairs, Thomas F. Imperiale, M.D., a VA and Regenstrief Institute clinician-researcher, is developing and validating a model to predict risk for colon cancer in those under 50 with no family history of the disease.
"We should be moving from an age-based system of screening for colon cancer to one that is risk-based because age is only one factor that contributes to risk," said Dr. Imperiale. "In our study we are identifying demographic, physical, and clinical factors that are different in people younger than 50 with colon cancer compared to those without colon cancer. These factors make them more comparable to those 50 and over.
"There have been calls to lower the age for routine colon cancer screening below age 50, but doing that doesn’t make sense at this point. It would simply be a reactive response that would likely result in net harm because we would be screening so many people unnecessarily and placing those with small adenomas into surveillance programs younger so they would have more lifetime colonoscopies – nearly all of them unnecessary. At this point, lowering the screening age would be time consuming and expensive and not necessarily good medicine."
Building upon his previous work, Dr. Imperiale's new retrospective study uses de-identified information from the electronic medical records of veterans from across the country age 35 to 49 with colon cancer and contrasting them with the medical records of two disease-free control groups of individuals under 50 with no family history of the disease. One of these control groups is comprised of veterans who have undergone colonoscopy and the other group of those who have not. All individuals whose records are being reviewed received health care from the VA between 2008 and 2014.
Age and sex are among the demographic factors being evaluated. Potential clinical risk factors under investigation are body mass index, cholesterol and triglyceride levels, blood pressure readings, as well as medical history. Lifestyle factors being studied include details on smoking and alcohol use, exercise, and occupation.
The researchers will determine which factors differ between cases with colon cancer and controls without colon cancer. According to Dr. Imperiale, who also holds appointments with the Indiana University Melvin and Bren Simon Cancer Center and the IU School of Medicine, this has not been previously studied in people under 50.
"The VA is one of very few healthcare systems where this work could be done," he said. "The VA's electronic medical record systems are so broad and deep we should able to discover candidate factors that will allow us to identify a subgroup of people under age 50 whose risk is comparable to older adults. For this group we could recommend some type of "early" screening — not necessarily colonoscopy — but perhaps blood stool test or another less invasive test before age 50."
In June 2016 the U.S. Preventive Services Task Force updated its recommendation for commencement of colon cancer screening at age 50. It advised that the decision to screen adults age 76 to 85 should be an individual one, taking into account the patient's overall health and prior screening history. No guidelines were given for those under 50.
Work on the three-year nearly $900,000 study is commencing this summer.