Colorectal Cancer

Colorectal Cancer (Large Intestine and Rectum Cancer)

What is Colorectal Cancer?

Colorectal cancer occurs when healthy cells in the colon or rectum start to change, growing uncontrollably and forming a tumor. This tumor may be benign (non-cancerous) or malignant (cancerous). The process can take years to develop, with both genetic and environmental factors playing a role.

Structure of the Large Intestine and Rectum

The large intestine is part of the digestive system, consisting of the colon and rectum. Its primary function is to convert digested food into stool. The colon (large intestine) is about 150 cm (5 to 6 feet) long, while the rectum forms the final 6 inches of the large intestine.

Colorectal Polyps

Polyps are benign growths found in the colon or rectum. Some types of polyps can eventually become cancerous. A colonoscopy can help detect and remove these polyps before they turn into cancer.

Statistics

In India, around 31,646 new cases of colon cancer and 28,260 new cases of rectal cancer are diagnosed annually. Colon cancer ranks 13th, and rectal cancer ranks 16th among all cancers in India. Additionally, 19,236 people die annually from colon cancer and 16,149 from rectal cancer.

Survival Rate

In the United States, the 5-year survival rate for colorectal cancer is 65%.

Risk Factors

Several factors increase the risk of developing colorectal cancer, though these do not necessarily cause it directly:

• Age: The risk increases as people age, with most cases occurring after age 50. However, younger cases have been rising recently.
• Gender: Colorectal cancer is more common in men.
• Family History: Having a first-degree relative (parent, sibling, or child) with colorectal cancer increases the risk. Around 5-10% of colorectal cancers result from genetic mutations.
• Inherited Conditions: Genetic disorders like Lynch syndrome, Familial Adenomatous Polyposis (FAP), and others can raise the risk of colorectal cancer.
• Inflammatory Bowel Disease (IBD): Conditions like ulcerative colitis or Crohn’s disease, which cause chronic inflammation in the colon, increase cancer risk.
• Adenomatous Polyps: While not all polyps become cancerous, adenomatous polyps have a higher likelihood of turning into cancer over time.
• Obesity and Diet: Lack of exercise and diets high in processed or red meat increase colorectal cancer risk.
• Smoking and Diabetes also contribute to a higher risk.

Prevention

Early detection through colonoscopy to remove polyps can help prevent colorectal cancer. Additionally, maintaining a healthy weight, quitting smoking, and making dietary changes can reduce the risk.

Screening for Colorectal Cancer

Screening helps detect cancer in individuals without symptoms. It is recommended for:

• Individuals with a history of colorectal cancer or adenomatous polyps.
• Those with first-degree relatives who had colorectal cancer.
• People with chronic inflammatory bowel disease.

Screening Methods

• Colonoscopy: This endoscopic test allows doctors to view the colon and remove any suspicious polyps or tissue samples (biopsies).
• Fecal Occult Blood Test (FOBT) and Fecal Immunochemical Test (FIT): These tests check for hidden blood in stool, a potential sign of colorectal cancer.

Symptoms

The symptoms of colorectal cancer are often similar to those of other common conditions:

• Diarrhea or constipation
• A feeling of incomplete bowel movement
• Blood in the stool
• Abdominal discomfort
• Unexplained weight loss
• Constant fatigue
• Unexplained anemia (iron deficiency)

Diagnosis

• Colonoscopy: A thorough examination of the colon using an endoscope. Biopsies can be taken if abnormalities are found.
• Biopsy: The only definitive way to diagnose cancer by examining tissue under a microscope.
• Biomarker Testing: Molecular tests to study specific genes or proteins involved in cancer, such as mismatch repair deficiency (dMMR).
• Other Tests: Blood tests (CBC, CEA), CT scan, MRI, PET-CT, Ultrasound, and Chest X-ray may be used for a more comprehensive diagnosis.

Treatment

1. Surgery: Removal of the tumor and surrounding healthy tissue (margin) is the primary treatment for colorectal cancer. Surgery can be done laparoscopically or robotically. In some cases, patients may require a colostomy, a procedure where the colon is diverted through an opening in the abdomen.
2. Radiation Therapy: High-energy radiation is used to kill cancer cells. It is often combined with chemotherapy, called chemoradiation, to increase the effectiveness of treatment. Radiation side effects may include fatigue, skin irritation, and diarrhea.
3. Chemotherapy: Uses drugs to destroy cancer cells. Some commonly used drugs for colorectal cancer include:
• Capecitabine (Xeloda)
• Fluorouracil (5-FU)
• Irinotecan (Camptosar)
• Oxaliplatin (Eloxatin)
• Trifluridine/tipiracil (Lonsurf)
Side effects of chemotherapy can include nausea, fatigue, vomiting, diarrhea, and hair loss.
4. Targeted Therapy: This treatment targets specific genes or proteins in cancer cells. Drugs used in targeted therapy for colorectal cancer include:
• Bevacizumab (Avastin)
• Fruquintinib (Fruzaqla)
• Cetuximab (Erbitux)
• Panitumumab (Vectibix)
5. Immunotherapy: Uses the body’s immune system to attack cancer cells. Drugs used in colorectal cancer immunotherapy include:
• Pembrolizumab (Keytruda)
• Nivolumab (Opdivo)
• Dostarlimab (Jemperli)