DENVER — The general guidelines for colorectal cancer screenings have long called for regular check-ups beginning at age 50, but as colorectal cancer rates rise among young people, health experts are now urging Americans to begin regular screenings at age 45.

“Moving the start of screening back to age 45 for the average risk population is a considerable change,” says study co-author Andrea Dwyer, director of the Colorado Colorectal Screening Program at the University of Colorado Cancer Center. “If everyone followed screening recommendations based on risk, we could cut colorectal cancer mortality by at least a half, with some estimates suggesting mortality would be cut up to 70 percent.”

Each year, 140,000 Americans are diagnosed with colorectal cancer and 50,000 Americans die from it.

To determine the new screening age, Dwyer and her team used a mathematical model called MISCAN. The researchers compared the benefits — or the instances that cancer is detected via colonoscopy — with the burden of going through a colonoscopy. They wanted to find an optimal age that would produce the highest percentage of cancer detection per colonoscopy.

“Think of it this way,” Dwyer says, “if screening started at age 20, you’d have maximum benefit but also a huge burden. It would be inefficient – we would find very few cases of cancer per colonoscopy. On the other hand, if screening started at age 60, you’d have minimal burden but also minimal benefit – we would be missing some cancers and finding others too late. The goal of screening guidelines is to find that sweet spot where there is the most benefit with the least burden.”

Their guidelines now recommend regular colonoscopies every ten years between the ages of 45 and 75. Meanwhile, researchers hope to pinpoint why so many more younger people are being diagnosed with colorectal cancer than in generations past.

“We used to think that young colorectal cancer was genetically different than the disease found in older patients. But now we’re finding this might not always be the case. It’s showing up younger and no one knows why,” Dwyer says. “Researchers have explored the usual things – obesity, tobacco, alcohol – but none of those fully explain the increase. Now people are examining anything they can think of that could influence this early risk – sugar, tap water, lifestyle, even the microbiome. I think there’s something very different for a 65-year-old who gets it versus a 25-year-old who gets it, but right now we just don’t know what that thing is.”

The answer could one day lead to major strides in the fight against the disease.

The full study was published May 30, 2018 in the journal Cancer.

About Ben Renner

Writer, editor, curator, and social media manager based in Denver, Colorado. View my writing at

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