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Colon Cancer

Overview

The colon, also called the large intestine, is the last part of the digestive system (gastrointestinal tract). Its main role is to absorb water and salts from food after digestion and to form faeces (stools) for excretion. The colon has different sections (segments). The last part of the colon is called the rectum, which terminates externally through the anal canal. Colon cancer (also called colorectal cancer when it involves the rectum) develops when abnormal cells grow uncontrollably in the lining of the colon. It is one of the most common cancers worldwide, being the 3rd most common in men and the 2nd most common in women. With early detection and timely treatment, colon cancer can often be treated successfully.

The main types of colon cancer include:

  • Adenocarcinoma: The most common type, accounting for over 90% of cases, originating in the glandular cells lining the colon and rectum.
  • Carcinoid tumours: Develop in the hormone-producing cells of the colon.
  • Gastrointestinal stromal tumours (GISTs): Rare growths starting in muscle or connective tissue.
  • Lymphomas: Cancers that begin in the immune system cells of the colon.

Colon cancer may present with the following symptoms:

  • Abdominal pain/discomfort, cramps, or a feeling of tightness
  • Change in bowel habits (such as increasing constipation or alternating constipation and diarrhoea)
  • Unexplained weight loss
  • Presence of anaemia (low haemoglobin) on a regular blood test
  • Blood in the stool (bright red or even dark black/brown)
  • Fatigue and tiredness
  • Nausea or loss of appetite
  • In some cases, colon cancer presents as an emergency with:
    • Intestinal obstruction (blockage of stool, causing abdominal swelling, severe pain, and vomiting)
    • Heavy bleeding from the tumour
    • Perforation (occasionally the tumour may rupture the abdominal wall, causing a dangerous and life-threatening infection)

  • Age: Risk increases after 50, though younger people can also be affected.
  • Family history and inherited syndromes such as Lynch Syndrome (hereditary non-polyposis colorectal cancer, HNPCC)
  • Polyposis syndromes/familial polyposis syndromes: Genetic conditions causing the growth of multiple polyps (small abnormal growths) in the colon, which may turn into cancer
  • Ulcerative colitis: Long-standing inflammation of the colon increases cancer risk
  • Colon polyps: Isolated polyps of the colon also increase the risk of colon cancer
  • Lifestyle factors: Smoking, obesity, sedentary habits, low-fibre high-fat diet, high intake of red or processed meat.

Colorectal cancer is often diagnosed via a combination of the following techniques:

  • Screening Tests:
    • Colonoscopy: A flexible camera tube used to view the inside of the colon; the gold standard for detecting polyps and tumours.
    • Faecal occult blood test (FOBT) or faecal immunochemical test (FIT): Detects hidden blood in stool.
  • Imaging Studies:
    • CT colonography (virtual colonoscopy).
    • MRI and CT scans for staging and detecting metastases.
  • Biopsy: Tissue samples taken during colonoscopy to confirm cancer diagnosis.
  • Blood tests: To evaluate tumour markers such as CEA (carcinoembryonic antigen) to monitor treatment response.

Treatment options depend on the stage, location, and patient factors:

  • Early-stage cancer:
    • Polypectomy: Removal of polyps during a colonoscopy.
    • Endoscopic mucosal resection (EMR): For larger, localised tumours.
  • Locally advanced cancer:
    • Surgery:
      • Open, Laparoscopic, or Robotic approaches for tumour removal.
      • Colectomy: part of the colon containing cancer is removed.
    • Neoadjuvant therapy: Chemotherapy or radiotherapy before surgery to shrink tumours.
  • Advanced cancer:
    • Chemotherapy: Used to shrink tumours or as adjuvant therapy post-surgery.
    • Targeted therapy: Monoclonal antibodies (e.g., bevacizumab) targeting cancer pathways.
    • Immunotherapy: Boosts the body’s immune system, used in certain patients with high microsatellite instability (MSI-H).
    • Palliative care: To manage symptoms and improve quality of life in metastatic cases.

You should consult a doctor if you notice persistent changes in your bowel habits, blood in your stool, unexplained abdominal pain, or unintentional weight loss. Early detection through screening is crucial, especially for people over 50 years or those with a family history of colorectal cancer.

Although colon cancer cannot always be prevented, risk can be reduced by:

  • Eating a balanced diet rich in fruits and vegetables; reducing the consumption of red and processed meats.
  • Exercising regularly and maintaining a healthy weight.
  • Avoiding smoking and limiting alcohol consumption.
  • Undergoing recommended screening tests (such as colonoscopy) after age 45–50 years, or earlier if you have risk factors.

If colorectal cancer is suspected or confirmed, several specialists may be involved:

  • Gastroenterologist: Performs colonoscopies and manages early detection.
  • Colorectal surgeon: Performs surgery for tumour removal.
  • Oncologist: Provides chemotherapy, targeted therapy, or immunotherapy.

In most cases, care is coordinated by a multidisciplinary team, ensuring a personalised treatment plan for each patient.

Disclaimer:

The information in this Health Library is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any questions about a medical condition or before starting any treatment. Use of this site and its content does not establish a doctor–patient relationship. In case of a medical emergency, call your local emergency number or visit the nearest emergency facility immediately.