Lowering the Age For Colorectal Cancer Screening
Dec 14, 2020 Nicole Levine
The rate of colorectal cancer among adults under age 50 has steadily climbed in the last 20 years, and scientists are still grappling with understanding the reasons why.
A combination of risk factors—obesity, lifestyle, environment, genetics—likely contributes to younger people becoming more likely to develop colorectal cancer, even though the overall rates of the disease have been decreasing.
"Colonoscopy is the best screening tool and has the added advantage of being preventive in that polyps found during the procedure can be removed."
In October 2020, the U.S. Preventive Services Task Force—a panel of federally appointed medical experts who determine which screenings would be covered by insurance under the Affordable Care Act—recommended the age for colorectal cancer screening to drop from 50 to 45 years old. The increased incidence among people in their 40s, and the disparities in outcomes experienced by minority groups, are among the motivating factors for the change.
"Not only are we seeing more people under 50 diagnosed with colorectal cancer, their cancers can be more advanced, which may lead to more negative outcomes," says Jane Catherine Figueiredo, PhD, director of Community and Population Health Research at Cedars-Sinai. Figueiredo is the leader of the nation's largest study on the prevention and treatment of colorectal cancer in Latinos. "Because we generally don't screen people under 50, early-stage cancers in this group are often missed unless they are experiencing symptoms, and even those experiencing symptoms may be misdiagnosed with other conditions, such as hemorrhoids."
Colonoscopy is the gold standard for screening, especially because small polyps can be removed during the procedure before they turn into cancer, a practice that has contributed to lower rates of colorectal cancer in older adults.
"Colonoscopy is the best screening tool and has the added advantage of being preventive in that polyps found during the procedure can be removed," says Megan Hitchins, PhD, an associate professor in the Department of Biomedical Sciences.
But there's a catch: They're expensive, they require a couple of days of preparation for the patient and younger people are reluctant to get them. Cedars-Sinai investigators are seeking ways to overcome obstacles to screening on multiple fronts.
Building a better blood test
Hitchins is researching alternative screening methods for people under 50—work funded by a grant from the Colorectal Cancer Alliance. While colonoscopy is the best method, others are also approved, such as an at-home test that requires a stool sample. One blood test that detects tumor DNA in the blood is also approved—however, the test looks only for one marker.
Hitchins' lab is working on tests that will identify more markers in the blood and will detect them even at low levels. These tests could help diagnose cancer at an early stage—when it's most treatable.
Screening with a blood test is attractive for many reasons, Hitchins says. Younger people require stronger sedation for a colonoscopy. The downtime for preparing for a colonoscopy—which could require time off work—can be a barrier for some. Others might never submit to a fecal test or colonoscopy for religious or cultural reasons.
Determining who needs screening most
One benchmark the medical community is reaching for is 80% screening for colorectal cancer using any method—colonoscopy, fecal test or blood test. At the same time, over-testing can cause its own set of problems in the form of unnecessary procedures or the stress of dealing with a false positive test for cancer.
Currently, screening is based on two factors: age and family history. Figueiredo and her team are working on creating models for colorectal cancer that are based on many factors.
"Our goal is to ensure that the younger people at higher risk get the screening they need, while avoiding over-screening in the general population," Figueiredo says.
Her team is seeking ways to incorporate race, ethnicity, genetics, gender and lifestyle factors into the equation.
"Unfortunately, early disease risk models were almost exclusively based on white populations. But because our genetic profiles vary across populations, those models may not perform as well in other populations, which may drive healthcare inequities," says Figueiredo.
In the U.S., Latinos have higher rates of early-onset colorectal cancer and tend to have more advanced disease when they're diagnosed compared to non-Hispanic whites. Black Americans have a 20% higher incidence of colon cancer than non-Hispanic white people in the U.S. and are 40% more likely to die of the disease.
"Lowering the age for screening is an important step in lowering colorectal cancer rates," Figueiredo says. "It's one step in the larger efforts to expand screening modalities and improve access to cancer screening and care."