How we learned to prevent it
In the 1970s pathologists at London's St Mark's Hospital, including Basil Morson, established that most colorectal cancers grow from adenomatous polyps. In 1990 Johns Hopkins researcher Bert Vogelstein showed that mutations in APC, KRAS, and p53 accumulate in sequence—now a textbook model of cancer genetics. The 1993 National Polyp Study found that removing polyps during colonoscopy cut cancer incidence by 76–90%, and screening spread worldwide. Katie Couric's on-air colonoscopy in 2000 famously boosted screening rates in the U.S.
Symptoms and risk factors
Early on there are usually no symptoms. Later signs include rectal bleeding or dark stools, a change in bowel habits (new constipation or diarrhea), narrower stools, feeling you haven't emptied, and unexplained anemia or weight loss—often mistaken for hemorrhoids. Risk factors include red and processed meat, obesity, alcohol, smoking, inactivity, family history, and inflammatory bowel disease. Cases in adults under 50 are rising, which led the USPSTF to lower the starting age for screening to 45 in 2021.
Screening, treatment, and prevention
Options include colonoscopy every 10 years, a yearly fecal immunochemical test (FIT), or a stool DNA test (Cologuard) every 1–3 years; any positive stool test needs a follow-up colonoscopy. Colonoscopy lets doctors remove polyps on the spot. Early cancers are often cured with endoscopic or laparoscopic surgery; advanced cases add chemotherapy, targeted drugs, and, for rectal cancer, radiation. A fiber-rich diet, less processed meat, regular exercise, and not smoking all lower risk.
This article is general health information and is not a substitute for diagnosis or treatment. If symptoms persist, see a doctor.
FAQ
- Is there an alternative to colonoscopy prep?
- Stool tests and CT colonography exist, but a positive result still means a colonoscopy.
- Does rectal bleeding mean cancer?
- Usually it's hemorrhoids, but get checked if you're over 40 or it keeps happening.
Sources reviewed: 2026-10-26
References
- U.S. Preventive Services Task Force. (2021). Screening for colorectal cancer: Recommendation statement. JAMA, 325(19), 1965–1977.
- Fearon, E. R., & Vogelstein, B. (1990). A genetic model for colorectal tumorigenesis. Cell, 61(5), 759–767.
- Siegel, R. L., et al. (2025). Cancer statistics, 2025. CA: A Cancer Journal for Clinicians, 75(1).