Colon Cancer
Cancer of the large bowel — highly curable when detected through screening before symptoms appear.
Overview
Colon cancer is part of colorectal cancer, the 4th most common UK cancer. Most arise from adenomatous polyps over 10–15 years, giving a long window for screening. Population FIT screening (every 2 years from age 50–74) reduces mortality by 25–30%. Survival exceeds 90% at stage 1 and falls below 15% at stage 4.
Symptoms
- • Change in bowel habit (looser, more frequent stools) over 4–6 weeks
- • Rectal bleeding or blood mixed through the stool
- • Iron-deficiency anaemia, especially in men or postmenopausal women
- • Abdominal pain, bloating or a palpable mass
- • Unexplained weight loss or fatigue
Risk factors
- • Age >50
- • Family history of colorectal cancer or adenomas
- • Processed/red meat, low fibre, alcohol, obesity, smoking, inactivity
- • Type 2 diabetes
Causes
- • Sporadic adenoma-carcinoma sequence (~75%)
- • Inherited syndromes: Lynch, familial adenomatous polyposis, MUTYH-associated polyposis
- • Inflammatory bowel disease (long-standing colitis)
🚨 Red flags — seek urgent care
- • Rectal bleeding with change in bowel habit
- • Iron-deficiency anaemia with no obvious source
- • Palpable abdominal or rectal mass
- • Bowel obstruction: pain, distension, vomiting, absolute constipation
When to seek care
- • Any persistent change in bowel habit or bleeding for >3 weeks
- • Always engage with FIT screening invitations
- • Family history meeting criteria for genetic referral
Diagnosis
- • Faecal Immunochemical Test (FIT) ≥10 µg/g triggers urgent colonoscopy
- • Colonoscopy with biopsy — gold standard
- • CT colonography if colonoscopy not tolerated
- • Staging: CT chest/abdo/pelvis, CEA, MRI rectum (if rectal)
- • Mismatch repair / MSI testing on all colorectal cancers
Treatment
- • Surgery: laparoscopic/robotic colectomy with regional lymphadenectomy
- • Adjuvant chemotherapy (oxaliplatin/fluoropyrimidine) for stage III and high-risk stage II
- • Targeted therapy in metastatic disease: anti-EGFR (cetuximab, RAS wild-type), anti-VEGF (bevacizumab), BRAF inhibitors
- • Immunotherapy (pembrolizumab) for MSI-high tumours
- • Liver/lung metastasectomy in selected cases — potentially curative
Prevention
- • Engage with FIT screening every 2 years from age 50–74
- • High-fibre diet, limit processed/red meat and alcohol
- • Maintain healthy weight, regular activity, stop smoking
- • Aspirin reduces risk in selected high-risk groups (e.g. Lynch syndrome)
Complications
- • Bowel obstruction or perforation
- • Liver, lung, peritoneal metastases
- • Surgical: anastomotic leak, stoma complications
- • Chemotherapy: neuropathy, neutropenia
Prognosis
5-year survival: ~95% stage I, ~85% stage II, ~65% stage III, ~12% stage IV — heavily dependent on early detection.
Education & self-care
Colon cancer is one of the most preventable cancers. Screening, polyp removal and prompt investigation of symptoms save lives.
Frequently asked questions
Is FIT screening accurate?
It detects most cancers and many high-risk polyps. A negative test does not exclude cancer — report new symptoms.
Do polyps always become cancer?
No — but some types do over years. Removing them at colonoscopy prevents cancer.
I am under 50 with bleeding — should I be worried?
Most cases are haemorrhoidal, but early-onset colorectal cancer is rising. See your GP.