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Colon cancer

Overview

Colon cancer, also known as colorectal cancer, is a type of cancer that begins in the large intestine (colon) or the rectum, both parts of the digestive system. It typically develops from abnormal growths called polyps on the inner lining of the colon or rectum, which can turn into cancer over time.

Several factors can increase the risk of developing colon cancer, including:

  • Age: The risk increases with age, especially after 50.
  • Family history: A family history of colon cancer or certain inherited genetic conditions, such as Lynch syndrome or familial adenomatous polyposis (FAP), increases the risk.
  • Lifestyle factors:
    • A diet high in red or processed meats.
    • Sedentary lifestyle.
    • Smoking and heavy alcohol consumption.
  • Medical conditions:
    • Inflammatory bowel diseases like Crohn’s disease or ulcerative colitis.
    • Type 2 diabetes.

In the early stages, colon cancer may not cause noticeable symptoms. As the cancer progresses, the following symptoms might occur:

  • Blood in the stool (either bright red or dark)
  • Unexplained weight loss
  • Persistent abdominal pain or discomfort
  • Changes in bowel habits (e.g., diarrhoea or constipation)
  • Feeling that the bowel does not empty completely
  • Fatigue

A colon cancer diagnosis generally involves a series of tests and procedures to confirm the presence of cancer and determine its stage. The steps in the diagnostic process typically include:

  • Physical examination: The doctor might conduct a physical exam, including a digital rectal exam (DRE), where the physician checks for abnormalities in the rectum.
  • Screening tests:
    • Faecal occult blood test (FOBT) or Faecal immunochemical test (FIT): These tests detect small amounts of blood in the stool that may not be visible to the naked eye. Blood in the stool could be a sign of cancer or polyps.
    • Colonoscopy: This is the gold standard for colon cancer screening. It involves inserting a flexible tube with a camera (colonoscope) into the rectum to view the inside of the colon. If any abnormal areas, such as polyps or tumours, are found, they can be biopsied (sampled for further analysis).
  • Imaging tests:
    • CT Colonography (virtual colonoscopy): This imaging test uses CT scans to create detailed images of the colon and rectum and can detect abnormal growths. However, if abnormalities are found, a traditional colonoscopy may be required for biopsy.
    • CT or MRI: These may be used to assess whether the cancer has spread to other organs like the liver, lungs, or lymph nodes.
  • Biopsy: If a suspicious area is found during colonoscopy or imaging, a biopsy is performed to confirm whether the tissue is cancerous. This involves taking a small sample of the tissue and examining it under a microscope.
  • Staging tests: Once cancer is confirmed, additional tests are conducted to determine the stage of the cancer, which describes how far it has spread. This is crucial for determining the best treatment approach. Staging tests can include:
    • Endoscopic ultrasound: To check for the spread of cancer to nearby lymph nodes or the wall of the colon.
    • PET scan: To detect cancer spread to distant organs.
    • Blood tests: Including the CEA (Carcinoembryonic Antigen) test, which is sometimes used to monitor cancer or detect recurrence (though not used for initial diagnosis).
  • Genetic testing (in some cases): Genetic testing may be recommended, especially if there’s a family history of colon cancer or certain inherited genetic conditions (like Lynch syndrome or familial adenomatous polyposis). Genetic mutations can sometimes influence treatment decisions and the likelihood of recurrence.

Treatment for colon cancer depends on the stage of the disease and may involve one or a combination of the following:

  • Surgery: Removing the tumour or part of the colon (colectomy). In some cases, a colostomy or ileostomy may be required.
  • Chemotherapy: Drugs used to kill cancer cells or shrink tumours, either before or after surgery.
  • Radiation therapy: Often used in rectal cancer or to shrink tumours before surgery.
  • Targeted therapy & immunotherapy: These newer treatments target specific proteins or genes involved in cancer cell growth, or help the immune system fight the cancer.

Colon cancer is one of the most preventable types of cancer through screening and lifestyle changes. It's typically recommended to begin screening at age 45, but those with a family history of colon cancer may need to start earlier.

  • Screening: Regular screening can help detect precancerous polyps or early-stage cancers. The most common screening tests include:
    • Colonoscopy: A procedure that allows doctors to view the inside of the colon and remove polyps during the same procedure.
    • Stool tests: Such as the faecal immunochemical test (FIT) or stool DNA test.
    • CT colonography (virtual colonoscopy) and sigmoidoscopy are alternatives in certain cases.
  • Lifestyle changes:
    • Eating a diet rich in fruits, vegetables, and whole grains.
    • Exercising regularly.
    • Avoiding smoking and limiting alcohol consumption.
    • Maintaining a healthy weight.
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