Overview
Colorectal (colon and rectal) cancer is cancer of the large intestine. Most begin as small, non-cancerous polyps that grow on the inner lining of the colon and may become cancerous over years. Detecting and removing polyps during screening can prevent cancer developing altogether.
How common is it?
Colorectal cancer is the fourth most common cancer in the UK with about 42,000 new cases per year. It is the second most common cause of cancer death.
Causes and risk factors
Most colorectal cancers develop from polyps. DNA changes in colon cells accumulate over years due to a combination of age, diet, lifestyle, and genetic factors.
Common risk factors
- Age over 50
- Diet high in red or processed meat
- Low fibre intake
- Obesity and low physical activity
- Smoking and excess alcohol
- Family history of colorectal cancer or polyps
- Inflammatory bowel disease (Crohn's or ulcerative colitis)
- Inherited syndromes: Lynch syndrome, FAP
Symptoms
- Blood in stools or rectal bleeding
- Change in bowel habits lasting more than 3 weeks (looser stools, increased frequency)
- Unexplained weight loss
- Abdominal pain, cramping, or discomfort
- Feeling that the bowel has not fully emptied
- Unexplained anaemia causing fatigue
- Many early cancers cause no symptoms at all
When to see a doctor
See a doctor promptly for blood in stools, a persistent change in bowel habit, or unexplained weight loss. These are urgent symptoms requiring 2-week referral for investigation.
Diagnosis
Colonoscopy is the gold standard and allows biopsy and polyp removal simultaneously. CT colonography (virtual colonoscopy) is an alternative. Stool testing for faecal occult blood is used in NHS screening. CT scan stages the disease.
Treatments
Surgery
Removal of the tumour and surrounding colon tissue is the main curative treatment. Laparoscopic (keyhole) surgery has largely replaced open surgery with faster recovery.
Chemotherapy
FOLFOX or CAPOX regimens are used after surgery for stage 3 cancers to reduce recurrence risk. Also used for metastatic disease.
Targeted therapy and immunotherapy
Bevacizumab, cetuximab, and immune checkpoint inhibitors are used for advanced cancers depending on molecular characteristics of the tumour.
Self-care and lifestyle
- Participate in NHS bowel cancer screening (faecal immunochemical test at age 50-74)
- Increase dietary fibre from wholegrains, vegetables, and pulses
- Limit red and processed meat intake
- Exercise regularly and maintain a healthy weight
Prevention
Bowel cancer screening finds polyps before they become cancer and is the most effective preventive measure. A healthy diet, active lifestyle, not smoking, and limiting alcohol all reduce risk.