How Common Is Colorectal Cancer?
Colorectal cancer (CRC) — cancer of the colon or rectum — is the third most common cancer diagnosis and the second leading cause of cancer death in the United States, with approximately 153,000 new cases and 52,000 deaths annually. The encouraging news: screening can detect precancerous polyps before they become cancer, and when CRC is caught at an early stage, the 5-year survival rate exceeds 90%.
Warning Signs and Symptoms
Early colorectal cancer often causes no symptoms, which is precisely why screening matters. When symptoms do appear, they may include:
- Blood in the stool (bright red or dark/tarry)
- A persistent change in bowel habits — diarrhoea, constipation, or narrowing of stool lasting more than a few weeks
- Rectal bleeding or the sensation that the bowel doesn't completely empty
- Abdominal cramping, pain, or discomfort
- Unexplained weight loss and fatigue (often from occult blood loss causing anaemia)
These symptoms overlap with many benign conditions (haemorrhoids, IBS), but any persistent change warrants medical evaluation.
Risk Factors
- Age — risk rises significantly after 45
- Personal or family history of colorectal cancer or polyps
- Inflammatory bowel disease (Crohn's or ulcerative colitis)
- Inherited syndromes — Lynch syndrome, familial adenomatous polyposis (FAP)
- Diet high in red and processed meat; low in fibre
- Obesity, physical inactivity, smoking, heavy alcohol use
- Type 2 diabetes
Screening Options
The US Multi-Society Task Force recommends starting screening at age 45 for average-risk adults (down from 50). Options include:
- Colonoscopy every 10 years — the gold standard; allows direct visualisation and removal of polyps in the same procedure
- Annual fecal immunochemical test (FIT) — a non-invasive stool test that detects blood; positive result requires follow-up colonoscopy
- FIT-DNA test (Cologuard) every 1–3 years — detects blood and abnormal DNA in stool
- CT colonography every 5 years — a "virtual colonoscopy" that images the colon by CT
- Flexible sigmoidoscopy every 5 years — examines only the lower third of the colon
Higher-risk individuals (personal/family history of CRC or polyps, IBD, Lynch syndrome) should begin screening earlier and more frequently — discuss timing with your doctor.
Prevention
Beyond screening, evidence-based strategies reduce CRC risk: eating a high-fibre diet (whole grains, vegetables, legumes), limiting red meat to <3 servings/week and avoiding processed meat, maintaining a healthy weight, getting 150+ minutes of moderate exercise per week, limiting alcohol, and not smoking. Regular aspirin use reduces polyp recurrence but carries bleeding risks — don't take it for cancer prevention without medical advice.