Colorectal Cancer

Types of Colorectal Cancer:

1. Adenocarcinomas: The most common type (around 95%), originating from glandular cells in the lining of the colon and rectum.
2. Carcinoid tumors: Develop from hormone-producing cells in the intestine.
3. Gastrointestinal stromal tumors (GISTs): Start in the connective tissue of the digestive tract.
4. Lymphomas: Cancers that begin in the immune system cells in the colon.
5. Sarcomas: Rare cancers that start in the muscle or blood vessels of the colon and rectum.

Risk Factors for Colorectal Cancer:

1. Age: Most cases occur in people aged 50 and older, but rates are rising among younger individuals.
2. Personal or family history: A history of colorectal polyps or cancer, or certain inherited conditions like familial adenomatous polyposis (FAP) or Lynch syndrome, increases the risk.
3. Inflammatory bowel disease (IBD): Conditions like ulcerative colitis and Crohn’s disease raise the risk of colorectal cancer.
4. Diet: A diet high in red or processed meats, and low in fiber, fruits, and vegetables, is associated with a higher risk.
5. Obesity: Being overweight or obese increases the likelihood of developing colorectal cancer.
6. Sedentary lifestyle: Lack of physical activity can contribute to a higher risk.
7. Smoking and alcohol: Long-term smoking and heavy alcohol consumption are linked to a higher incidence of colorectal cancer.
8. Type 2 diabetes: People with diabetes have an increased risk of colorectal cancer.

Symptoms of Colorectal Cancer:

Colorectal cancer may not cause symptoms in its early stages. When symptoms do appear, they may include:

• Changes in bowel habits: Persistent diarrhea, constipation, or narrowing of the stool that lasts more than a few days.
• Blood in the stool: Bright red or dark blood may appear in the stool.
• Abdominal pain or cramping: Discomfort or pain in the abdomen that does not go away.
• Unexplained weight loss: Losing weight without trying.
• Fatigue or weakness: Due to anemia from chronic blood loss.
• Incomplete bowel movements: A feeling that the bowel does not empty completely.

Diagnosis of Colorectal Cancer:

1. Screening tests:

   • Colonoscopy: The most effective screening tool, allowing doctors to examine the entire colon and rectum and remove polyps during the procedure.
   • Fecal occult blood test (FOBT) or Fecal immunochemical test (FIT): These tests check for hidden blood in the stool.
   • Stool DNA test: Examines stool samples for genetic mutations associated with colorectal cancer.
   • Sigmoidoscopy: Examines only the lower part of the colon and rectum.
   • CT colonography (virtual colonoscopy): A non-invasive imaging technique to visualize the colon.

2. Imaging tests:

   • CT scan or MRI: Used to assess the extent of cancer spread (staging).
   • PET scan: Helps detect the presence of cancer in other parts of the body.

3. Biopsy: If a suspicious area or polyp is found during a colonoscopy, a tissue sample is taken and examined under a microscope to confirm the presence of cancer.

Stages of Colorectal Cancer:

Colorectal cancer is staged based on how far it has spread:

• Stage 0 (Carcinoma in situ): Abnormal cells are found in the inner lining of the colon or rectum.
• Stage I: Cancer has grown into the inner layers of the colon or rectum but has not spread outside the wall.
• Stage II: Cancer has spread through the muscle layer to nearby tissues but not to lymph nodes.
• Stage III: Cancer has spread to nearby lymph nodes but not to other parts of the body.
• Stage IV: Cancer has spread to distant organs like the liver, lungs, or other sites (metastasis).

Treatment of Colorectal Cancer:

Treatment depends on the stage of the cancer and the patient’s overall health. Common treatments include:

1. Surgery:

   • Polypectomy: Removal of polyps during colonoscopy for early-stage cancer.
   • Colectomy: Partial or total removal of the colon. In some cases, an ostomy (stoma) may be necessary to divert stool.
   • Laparoscopic surgery: A minimally invasive surgery to remove part of the colon.
   • Metastasectomy: Removal of cancer that has spread to other organs (like the liver).

2. Chemotherapy:

   • Used to kill cancer cells or shrink tumors before surgery (neoadjuvant) or after surgery to eliminate remaining cancer cells (adjuvant).
   • Common drugs include 5-fluorouracil (5-FU), capecitabine, and oxaliplatin.

3. Radiation Therapy:

   • Often used for rectal cancer, either before surgery to shrink the tumor or after surgery to prevent recurrence.

4. Targeted Therapy:

   • Drugs like bevacizumab (Avastin), which targets cancer’s blood supply, or cetuximab and panitumumab, which target specific cancer cell proteins.

5. Immunotherapy:

   • Used for cancers with certain genetic mutations (e.g., MSI-H or dMMR). Pembrolizumab and nivolumab are examples of immunotherapy drugs that boost the body’s immune system to fight cancer.

Prevention of Colorectal Cancer:

1. Regular screening: Colonoscopy or other screening tests should begin at age 45 (or earlier for those at higher risk) to detect and remove polyps before they turn cancerous.
2. Healthy diet: A diet high in fiber (fruits, vegetables, whole grains) and low in red and processed meats is associated with a lower risk of colorectal cancer.
3. Exercise: Regular physical activity helps maintain a healthy weight and reduces cancer risk.
4. Limit alcohol and quit smoking: Reducing alcohol intake and avoiding smoking lower the risk of colorectal cancer.
5. Manage weight and diabetes: Keeping a healthy weight and managing diabetes can reduce the risk.

When to Seek Medical Attention:

If you experience symptoms such as persistent changes in bowel habits, blood in your stool, or unexplained weight loss, you should consult a doctor. Regular screening is also critical for early detection and treatment.

Conclusion:

Colorectal cancer is a preventable and treatable disease when detected early. Regular screening, a healthy lifestyle, and attention to risk factors can significantly reduce the likelihood of developing colorectal cancer. Early intervention through surgery, chemotherapy, and other treatments offers a high chance of survival, especially in the early stages of the disease.