Colorectal cancer used to be considered an older person’s disease. Doctors didn’t recommend screening until age 50 for years. But that picture is shifting fast.
More people in their 30s and 40s are now getting diagnosed. Colorectal cancer is now the top cancer killer in adults under 50. In 1995, only 27% of new cases were in people under 65. Today that number is 45%. Because of this shift, the recommended screening age dropped to 45 in 2021.
That change in screening age explains part of the rise, but not all of it. Cases were already climbing before 2021, and diagnoses in people under 45 are still increasing too.
Dr Shruti Patel, an oncologist at Stanford, says the trend isn’t just better detection. It’s a real increase, and it worries doctors across the field. She and Dr Curtis Chong started a clinic in 2025 just for patients diagnosed before 50, helping them with issues like fertility and career disruption during treatment.
What counts as early-onset?
Doctors use this term for cases found before age 45 or 50. Rectal cancer specifically is rising fast in younger people. It now makes up about a third of all colorectal cancer cases, up from a quarter twenty years ago.
Why is this increase happening?
Nobody has a clear answer. Genetics can’t explain a shift of this magnitude so fast, so scientists think something in our environment or lifestyle has changed. Poor diet and inactivity play a role, but don’t account for the full increase. Patel notes that many of her patients live healthier than most people, yet still get sick.
Rates are also higher among minority communities in the U.S., which is why Dr Chong is building a Spanish-language support programme at Stanford’s Redwood City site. Scientists are also studying the gut microbiome, the bacteria living in our intestines, to see if it plays a role.
Experts agree on one thing: the issue isn’t about young people making bad choices. Hidden exposures, like pesticides or chemicals in the food supply, might matter more than we realise.
Symptoms look the same but get missed
Warning signs include rectal bleeding, bowel changes, stomach pain, weight loss, fatigue and low energy. The issue is these signs Younger patients often dismiss these signs. in younger patients. Bleeding is mistaken for haemorrhoids. Cramps get blamed on stress or diet. As a result, young patients wait 40% longer for a diagnosis, and nearly 3 in 4 have already advanced disease by the time they’re diagnosed.
Doctors suggest tracking your bathroom habits weekly. If something changes for more than a few weeks, get it checked, and don’t hesitate to ask your doctor directly about young-onset cancer.
Screening guidelines
Screening guidelines say average-risk adults should start at age 45. If a parent or sibling had colorectal cancer, start 10 years earlier than their age at diagnosis. There are a few ways to screen. A colonoscopy every 10 years lets doctors examine the colon directly and remove any growths on the spot. At-home stool tests, like Cologuard or FIT, work every 1 to 3 years. Blood tests, like Shield, work every 3 years. If you already have symptoms, skip straight to a colonoscopy. It does double duty, catching problems and treating them at the same time.
Treatment
Treatment depends on the cancer’s stage, location and genetic makeup, not the patient’s age. Options include surgery, chemotherapy, radiation and, increasingly, immunotherapy, which trains the immune system to fight the tumour. New drug classes are also entering trials.
Lowering your risk
Some risk factors can be controlled: diet, exercise, alcohol use, weight and smoking. Others cannot: age, family history and inherited gene mutations like Lynch syndrome. However, these genetic syndromes only explain 20% of early-onset cases.
Scientists are also investigating newer potential risks, such as microplastics, childhood antibiotic use, and agricultural chemicals, although none of these have been proven yet. yet.
The key takeaway is to be aware of your body, not dismiss any symptoms, and consult a doctor promptly if something seems amiss.
