Rising Early-Onset Colorectal Cancer and What Younger Adults Need to Know

Colorectal cancer has long been viewed as a disease primarily affecting older adults, but rising incidence in younger populations is challenging that perception and raising new questions about risk factors, diagnosis, and prevention. To better understand this shift, we spoke with Dr. Jeremy Kortmansky, a medical oncologist at Yale School of Medicine and Smilow Cancer Hospital, where he specializes in gastrointestinal cancers, including colorectal tumors.

Cure: Colorectal cancer has traditionally been considered a disease of older adults—how has that perception shifted as more younger patients are being diagnosed?

Kortmansky: It’s still predominantly a disease of older patients, but historically, a generation ago, patients under 50 made up about 10% of patients, and now under 50 makes up about 20% of patients. So there’s been a doubling across a generation of cases in those 50 and younger. Part of that is patients being diagnosed younger. The change in incidence is about 3% a year. And the older population is actually decreasing, likely a testament to screening colonoscopies and removing precancerous polyps before they become invasive cancer.

What are the leading theories behind why early-onset colorectal cancer is increasing, and which do you find most compelling?

I think they’re all compelling. There are a number of theories around lifestyle—an increase in sedentary behavior, generally poor diets, processed foods, high alcohol use, and lack of exercise. All of those are contributing by changing the microbiome. When you change the microbiome, there’s increased inflammation in the bowel and a breakdown of the intestinal barrier that separates our gut from the rest of the body, with effects on immune surveillance. There are also theories about earlier antibiotic exposure in life, both from illness and antibiotic-treated foods, and growing literature around microplastics affecting intestinal integrity and the microbiome. All of these are plausible explanations for the changes we’re seeing over the past generation.

Why are younger patients often diagnosed at later stages—are symptoms being missed, dismissed, or misunderstood?

I think some of that is the case. When you are younger, it is easier to misassign symptoms of cancer to more benign conditions. So changes in bowel habits, abdominal pain, bleeding—those need to be taken seriously and investigated sooner. But this may also be a biologically different disease. There are molecular differences, and even when you match stages, younger patients may behave more aggressively. So it’s not all just late diagnosis—there are likely biological factors as well.

What are the most important symptoms that both patients and clinicians should not ignore in younger adults?

Don’t ignore bleeding, don’t ignore bowel pain, and don’t ignore a change in bowel habits. If someone is usually regular and now has pain with bowel movements, or a change in stool caliber, those need to be taken seriously. These were historically triggers in older patients, and now they need to be triggers in younger patients as well. The screening age for average risk is now 45 instead of 50, but there should be exceptions for patients with family history, inflammatory bowel disease, or concerning symptoms.

Despite lowering the screening age to 45, gaps still exist—what are the biggest barriers preventing people from getting screened?

These guidelines are relatively recent, but colonoscopy is still a big undertaking. Getting time away from work or family to do the prep and procedure is a challenge, especially in younger populations. There are non-invasive options like Cologuard that can be helpful for average-risk patients, but we still need to keep emphasizing the importance of screening. We’ve also been hearing more stories of young public figures with colon cancer, and hopefully that helps reinforce that this is a deadly disease and screening is important.

Are there particular populations that are disproportionately affected by these screening gaps or rising incidence rates?

Generally, males are affected more than females, with a poorer prognosis, although those groups are coming closer together. The Black population has a higher risk and is more likely to present with later-stage disease. Smaller populations, like Pacific Islanders and Alaska Natives, also have higher incidence. And beyond that, social determinants of health matter—people don’t always have the flexibility to miss work for screening, and access to healthcare is not equal. Those are important barriers as well.

What changes—whether in awareness, clinical practice, or policy—do you think are most urgently needed to address this issue?

From a policy standpoint, screening is already an approved intervention, so access through insurance is generally not the issue. But people still need flexibility to take time off work for routine health maintenance. More importantly, we need to get the message out earlier—to gastroenterologists and primary care providers—to encourage screening and take symptoms seriously. The goal is to catch and remove precancerous polyps so patients never need to see an oncologist or surgeon.

What is the most important message you want patients—especially younger adults—to understand about preventing or catching colorectal cancer early?

It is a real problem, and it requires being proactive about screening and reporting symptoms. Knowing your family history is important, because a higher percentage of younger patients have hereditary cancer. Beyond that, treating your body well matters—diet low in processed foods and red meat, limiting alcohol, maintaining a healthy weight, and exercising regularly. About 50% of colon cancers are still related to modifiable lifestyle factors. It’s not 100% preventable, but we can control what we can.

Transcript has been edited for clarity and conciseness.

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