Colon Cancer
Colon Cancer: Malignant tumor of the colon, usually adenocarcinoma, commonly arising from adenomatous polyps through the adenoma-carcinoma sequence. Early detection by screening is very important.
Risk Factors
- Increasing age
- Family history of colorectal cancer / Lynch syndrome / FAP
- Adenomatous polyps, inflammatory bowel disease
- Diet high in red/processed meat, obesity, smoking, alcohol
Pathology
- Usually adenocarcinoma
- Often develops from a colonic polyp over time
Clinical Features
- Occult or overt blood in stool
- Change in bowel habits: constipation, diarrhea, narrow stools
- Iron deficiency anemia, fatigue, weight loss
- Abdominal pain or bowel obstruction in advanced disease
Right vs Left Colon Cancer
Right-sided: occult bleeding, iron deficiency anemia, weakness
Left-sided: change in bowel habits, colicky pain, obstruction, visible blood in stool
Diagnosis
- Colonoscopy with biopsy = diagnostic test of choice
- Staging done with imaging after histologic confirmation
- CEA may be used mainly for follow-up, not screening
Spread
- Spreads first to regional lymph nodes
- Common distant metastasis site: liver
- Lung metastasis may also occur
Management
- Surgical resection = main treatment for localized colon cancer
- Chemotherapy for node-positive or advanced disease
- Targeted therapy / immunotherapy may be used in selected advanced cases based on biomarkers
Prevention / Screening
- Screening helps detect polyps and early cancer
- Average-risk adults are generally advised to begin colorectal cancer screening at age 45
High-Yield Points
- Most colon cancers are adenocarcinomas
- Right colon = anemia
- Left colon = obstruction/change in bowel habits
- Liver is the most common metastatic sit
