RECTAL CANCER

Rectal Cancer is a type of cancer that develops in the rectum, which is the last several inches of the large intestine, just before the anus. It is often grouped together with colon cancer as “colorectal cancer,” but there are important differences in how rectal cancer is treated due to the anatomy of the rectum and its proximity to other organs and structures in the pelvis.

Types of Rectal Cancer

  1. Adenocarcinoma:

    • The most common type, accounting for about 95% of rectal cancers.
    • Arises from the glandular cells that line the rectum and produce mucus.

  2. Other Rare Types:

    • Carcinoid Tumors: Start in hormone-producing cells.
    • Gastrointestinal Stromal Tumors (GIST): Originate in the connective tissue of the rectum.
    • Lymphomas: Rarely, lymphomas can develop in the rectum.

Risk Factors

  • Age: Most cases occur in people over 50, though it can develop in younger people.
  • Family History: A family history of rectal cancer or polyps increases risk.
  • Genetic Syndromes: Conditions like Lynch syndrome and familial adenomatous polyposis (FAP) significantly raise the risk.
  • Personal History of Polyps or Cancer: Previous colorectal cancer or adenomatous polyps increase risk.
  • Inflammatory Bowel Disease: Chronic conditions like ulcerative colitis or Crohn’s disease increase risk.
  • Diet: Diets high in red and processed meats and low in fiber are linked to a higher risk.
  • Obesity: Being overweight or obese is associated with an increased risk.
  • Sedentary Lifestyle: Lack of physical activity increases risk.
  • Smoking and Alcohol: Long-term smoking and heavy alcohol use are risk factors.
  • Type 2 Diabetes: Individuals with type 2 diabetes have a higher risk of developing rectal cancer.

Symptoms

Rectal cancer symptoms can be similar to those of other gastrointestinal conditions, and they may include:

  • Changes in Bowel Habits: Persistent diarrhea, constipation, or a change in stool consistency, particularly narrower stools.
  • Rectal Bleeding: Blood in the stool, which may appear bright red or dark.
  • Abdominal Pain or Discomfort: Cramping, gas, or pain in the abdomen.
  • Feeling of Incomplete Bowel Evacuation: A sensation that the bowel doesn’t empty completely after a bowel movement.
  • Weakness and Fatigue: Often due to anemia caused by chronic blood loss.
  • Unexplained Weight Loss: Losing weight without trying can be a sign of cancer.
  • Iron-Deficiency Anemia: Caused by slow, chronic blood loss from the rectum.

Diagnosis

Diagnosing rectal cancer involves several steps:

  • Physical Examination: The doctor may perform a digital rectal exam to feel for any abnormalities in the rectum.
  • Colonoscopy: A procedure where a flexible tube with a camera (colonoscope) is inserted into the rectum to examine the entire colon and rectum. Polyps or suspicious areas can be biopsied.
  • Proctoscopy or Sigmoidoscopy: Similar to colonoscopy but focuses on the rectum and lower part of the colon.
  • Biopsy: Tissue samples taken during a colonoscopy or other procedures are examined under a microscope to confirm cancer.
  • Imaging Tests:
    • CT Scan or MRI: Provides detailed images of the abdomen and pelvis to assess the extent of the cancer.
    • Endorectal Ultrasound: Uses sound waves to produce images of the rectum and surrounding tissues, helping to determine the depth of cancer penetration.
    • PET Scan: Helps detect whether the cancer has spread to other parts of the body.
  • Blood Tests: Including tests for anemia and tumor markers like CEA (carcinoembryonic antigen).

Staging

Rectal cancer is staged based on the extent of the disease:

  • Stage 0 (Carcinoma in Situ): Cancer is only in the innermost lining of the rectum.
  • Stage I: Cancer has grown into the muscle layer of the rectum but has not spread outside the rectum.
  • Stage II: Cancer has grown through the muscle layer to the outermost layers of the rectum or surrounding tissues.
  • 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 distant lymph nodes.

Treatment

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

  • Surgery:

    • Local Excision: Removes small, early-stage tumors or polyps.
    • Low Anterior Resection (LAR): Removes the rectum while preserving the anal sphincter, allowing for normal bowel movements.
    • Abdominoperineal Resection (APR): Removes the rectum and anus, requiring a permanent colostomy (an opening in the abdomen for waste to exit the body).
    • Total Mesorectal Excision (TME): A precise surgical technique to remove the rectum and surrounding tissues, reducing the risk of recurrence.

  • Radiation Therapy:

    • Often used before surgery to shrink tumors or after surgery to eliminate remaining cancer cells.
    • Can also be used to relieve symptoms in advanced stages.

  • Chemotherapy:

    • Used before surgery (neoadjuvant) to shrink the tumor or after surgery (adjuvant) to reduce the risk of recurrence.
    • Also used to treat advanced-stage cancer.

  • Targeted Therapy:

    • Drugs that target specific molecules involved in cancer growth, such as VEGF inhibitors or EGFR inhibitors, may be used in advanced or recurrent cases.

  • Immunotherapy:

    • For certain types of advanced rectal cancer, particularly those with high microsatellite instability (MSI-H) or mismatch repair deficiency (dMMR).

  • Palliative Care:

    • Focuses on relieving symptoms and improving quality of life in advanced cancer cases.

Prognosis

The prognosis for rectal cancer varies depending on the stage at diagnosis. Early-stage rectal cancer has a high cure rate, with five-year survival rates around 90% for localized disease. However, survival rates decrease significantly if the cancer has spread to lymph nodes or distant organs. For metastatic rectal cancer (stage IV), the five-year survival rate is about 14%.

Prevention and Early Detection

  • Screening: Regular screening, such as colonoscopy, starting at age 45 (or earlier for those with a family history or other risk factors), is key to early detection and prevention.
  • Healthy Diet: A diet rich in fruits, vegetables, and whole grains, and low in red and processed meats may reduce risk.
  • Exercise: Regular physical activity is associated with a lower risk of rectal cancer.
  • Maintain a Healthy Weight: Avoiding obesity helps reduce the risk.
  • Limit Alcohol and Quit Smoking: Both smoking and excessive alcohol use are linked to an increased risk of rectal cancer.
  • Genetic Counseling and Testing: For individuals with a strong family history of rectal cancer or known genetic syndromes, genetic counseling and regular screening may be recommended.