COLON CANCER

Colon Cancer, also known as colorectal cancer when including rectal cancer, is a type of cancer that begins in the colon (large intestine) or rectum. It usually starts as a polyp, a small growth on the inner lining of the colon or rectum, which can become cancerous over time. 

Types of Colon Cancer

  1. Adenocarcinoma:

    • The most common type of colon cancer.
    • Originates in the glandular cells that line the colon and rectum.
    • Subtypes include:
      • Mucinous Adenocarcinoma: Produces mucus and is more aggressive.
      • Signet Ring Cell Carcinoma: Contains cells that resemble signet rings and is less common but aggressive.

  2. Other Types:

    • Squamous Cell Carcinoma: Rare in the colon, more common in the rectum.
    • Neuroendocrine Tumors: Rare tumors that start in neuroendocrine cells.
    • Sarcomas: Rare cancers arising from connective tissues.

Risk Factors

  • Age: Risk increases significantly after age 50.
  • Family History: A family history of colon cancer or polyps increases risk. Genetic conditions like Lynch syndrome or familial adenomatous polyposis (FAP) are linked to higher risks.
  • Personal History: Previous colon cancer or polyps increases the risk of developing new cancers.
  • Inflammatory Bowel Disease (IBD): Conditions like ulcerative colitis or Crohn’s disease increase risk.
  • Diet: Diets high in red or processed meats and low in fiber, fruits, and vegetables can increase risk.
  • Obesity: Being overweight or obese is associated with a higher risk.
  • Physical Inactivity: Lack of regular physical activity increases risk.
  • Smoking and Alcohol Use: Both are linked to a higher risk of colon cancer.

Symptoms

Colon cancer symptoms can be subtle or mistaken for other conditions but may include:

  • Changes in Bowel Habits: Persistent diarrhea, constipation, or a change in stool consistency.
  • Rectal Bleeding or Blood in Stool: Blood may appear bright red or dark.
  • Abdominal Pain: Persistent or crampy pain in the abdomen.
  • Unexplained Weight Loss: Losing weight without a known reason.
  • Fatigue: Persistent tiredness or weakness.
  • Feeling of Incomplete Bowel Emptying: A sensation that the bowel does not fully empty.

Diagnosis

Diagnosing colon cancer involves several steps:

  • Colonoscopy: A procedure where a flexible tube with a camera (colonoscope) is inserted into the rectum to view the colon and take biopsy samples.

  • Biopsy: Tissue samples taken during colonoscopy are examined under a microscope to confirm cancer.

  • Imaging Tests:

    • CT Scan (Computed Tomography): Provides detailed images of the colon and surrounding tissues to assess the extent of the cancer.
    • MRI (Magnetic Resonance Imaging): Offers detailed images and helps evaluate the extent of the disease.
    • PET Scan (Positron Emission Tomography): Detects cancer spread to other parts of the body.
    • Ultrasound: Sometimes used to assess the liver for metastases.

  • Blood Tests:

    • Complete Blood Count (CBC): To check for anemia, which can occur with bleeding.
    • Liver Function Tests: To assess liver health and check for metastasis.
    • Tumor Markers: Tests like CEA (carcinoembryonic antigen) may be used to monitor treatment response, though not typically used for initial diagnosis.

Staging

Colon cancer is staged based on how far the cancer has spread:

  • Stage 0: Cancer is confined to the inner lining of the colon (carcinoma in situ).
  • Stage I: Cancer has spread to the outer layers of the colon but not to nearby lymph nodes.
  • Stage II: Cancer has spread to nearby tissues but not to lymph nodes.
  • Stage III: Cancer has spread to nearby lymph nodes but not to distant organs.
  • Stage IV: Cancer has spread to distant organs, such as the liver, lungs, or other areas.

Treatment

Treatment for colon cancer depends on the stage, location, and overall health of the patient:

  • Surgery:

    • Colectomy: Removal of part or all of the colon. The type of surgery depends on the cancer’s location and extent.
    • Laparoscopic Surgery: Minimally invasive surgery using small incisions and a camera.
    • Colostomy: Sometimes a temporary or permanent stoma (opening) is created for waste to leave the body.

  • Chemotherapy:

    • Uses drugs to kill cancer cells or stop them from growing. Common drugs include 5-fluorouracil, leucovorin, and oxaliplatin.
    • Often used after surgery (adjuvant therapy) or before surgery (neoadjuvant therapy) to shrink tumors.

  • Radiation Therapy:

    • Primarily used for rectal cancer to shrink tumors before surgery or to alleviate symptoms in advanced cases.

  • Targeted Therapy:

    • Drugs that target specific molecules involved in cancer growth, such as anti-EGFR (epidermal growth factor receptor) therapies for certain types of colon cancer.

  • Immunotherapy:

    • Uses the body’s immune system to fight cancer, particularly for cancers with specific genetic mutations or high microsatellite instability (MSI-H).

Prognosis

The prognosis for colon cancer varies depending on factors such as the stage at diagnosis, the cancer’s grade, and the patient’s overall health. The overall five-year survival rate for colon cancer is about 64%, but this varies significantly based on the stage at diagnosis and treatment effectiveness. Early detection and treatment improve the chances of a favorable outcome.

Prevention and Early Detection

  • Screening: Regular screening is recommended for people starting at age 45 or earlier for those with risk factors. Methods include colonoscopy, stool tests, and flexible sigmoidoscopy.
  • Healthy Lifestyle: Eating a diet rich in fruits, vegetables, and whole grains, maintaining a healthy weight, engaging in regular physical activity, and avoiding tobacco and excessive alcohol can reduce risk.
  • Manage Risk Factors: Treating conditions like inflammatory bowel disease and addressing family history or genetic predispositions with a healthcare provider.

Early detection through screening and lifestyle changes are key components in reducing the risk of colon cancer and improving outcomes.