Colorectal cancer is no longer just a disease of older adults

Written by Erin Reau.

For years, colorectal cancer prevention has been one of medicine’s real success stories.

Since the 1990s, widespread screening, especially colonoscopy, has led to major drops in both diagnoses and deaths among adults age 50 and older.

And catching cancer early makes a huge difference: it allows for curative surgery, timely treatment and even removal of precancerous polyps before they ever become cancer.

But there’s a troubling twist to that success story— with one clinician seeing it more and more in real life.

According to Elena Stoffel, M.D., M.P.H., Professor of Internal Medicine and Human Genetics at Michigan Medicine, and a national leader in cancer genetics and prevention, colorectal cancer is rising fast in younger adults—and our health care system hasn’t fully caught up yet.

A concerning shift in who gets colorectal cancer

“We have really strong evidence that colon cancer screening saves lives,” Stoffel said.

"We’ve seen both colorectal cancer rates and deaths go down in people over 50 because we’re screening that group.”

At the same time, rates are climbing among people under 50.

“Millennials’ risk of colorectal cancer is estimated to be about four times higher than their grandparents,” Stoffel noted.

That shift has serious consequences.

Today, colorectal cancer is the leading cause of cancer-related death in people under 50, something that would have been almost unthinkable a generation ago.

Genetics explain some, but not most, cases

A big focus of Stoffel’s research is understanding how genetics contribute to early-onset colorectal cancer.

Over the past decade, her team and others have found that about 20% of young patients with colorectal cancer carry a known genetic risk factor.

Conditions like Lynch syndrome and familial adenomatous polyposis are critically important to identify, because they dramatically change how and when patients should be screened.

But there’s a catch.

“That also means that we don’t find a genetic explanation for four out of five young people with colorectal cancer,” Stoffel explained.

That gap has pushed researchers to look harder at environmental and lifestyle factors, with leading suspects to include chronic inflammation in diets, changes in the gut microbiome, exposure to environmental toxins, and even emerging concerns about microplastics.

Large studies, such as the Nurses’ Health Study, suggest that diets high in ultra-processed, pro-inflammatory foods may also increase colorectal cancer risk.

What’s more, colorectal cancer rates vary widely around the world, but they’re rising in many countries at once.

That points to shared changes in diet, food systems, and environmental exposures, rather than genetics alone.

Lowering the screening age helps, but it’s not the whole answer

In 2020–2021, screening guidelines were updated to recommend starting average-risk colorectal cancer screening at age 45 instead of 50.

That change expanded eligibility by about 20%.

It was an important step, but it doesn’t solve the whole problem, noted Stoffel.

“Half of our young colon cancer patients are actually under 45.”

Rather than continuing to lower the screening age across the board, she argues for better risk-based screening.

“Age 45 is just a number,” she said.

“Your colorectal cancer risk depends much more on family history and other risk factors than on a specific birthday.”

Family history: One of the most overlooked risk factors

Family history is one of the clearest—and most actionable—signals of increased risk, yet it’s often missed.

“If you have a close relative with colorectal cancer or large polyps, that needs to be part of the conversation with your care team,” Stoffel said.

Many of these patients should start colonoscopy at age 40, or 10 years earlier than the age at which their relative was diagnosed.

Family histories of other cancers matter too.

Some hereditary cancer syndromes affect multiple organs and recognizing them can mean starting screening much earlier—sometimes as young as 20 or 25.

Symptoms matter, no matter your age

Colorectal cancer is tricky because early disease often causes no symptoms at all.

That’s why screening is so important.

But when symptoms do show up, they’re too often brushed off in younger patients.

“No one is too young for colorectal cancer,” Stoffel said plainly.

Symptoms that should always be taken seriously include: