Colorectal carcinoma (CRC) refers to cancer originating in the mucosal lining of the colon or rectum. It is one of the most prevalent and preventable cancers globally. The disease often arises silently from precancerous polyps and, if undetected, can lead to life-threatening complications.
What is Colorectal Carcinoma?
Colorectal carcinoma is a malignant tumor that originates from the epithelial cells lining the colon or rectum. It accounts for:
- 65% of cases in the colon
- 35% in the rectum
The disease typically follows the adenoma-carcinoma sequence, where benign polyps transform into cancer over years due to genetic mutations.
Key Highlights
- Genetic and lifestyle factors play a major role
- Most cases begin as adenomatous polyps
- Early-stage cancers are curable with surgery
- Screening programs significantly reduce mortality
- 20% of CRC cases present as emergencies
Epidemiology
- More common in males (1.3:1 ratio)
- Incidence increases after age 50
- Higher rates in Western countries due to diet and lifestyle
- Lifetime risk is about 4–5%
Causes and Risk Factors
Major Predisposing Factors:
1. Personal history of adenomas or colorectal cancer2. Hereditary syndromes:
- Familial Adenomatous Polyposis (FAP)
- Lynch Syndrome (HNPCC)
- Juvenile polyposis
3. Family history of CRC (1st-degree relatives)
4. Inflammatory bowel disease (especially ulcerative colitis)
5. Obesity, diabetes, alcohol, red meat consumption
6.Cholecystectomy and renal transplantation
7. NSAIDs, physical activity, fiber, and calcium may be protective
Pathology of Colorectal Cancer
Macroscopic Appearance:
- Polyploid or ulcerating
- Annular (apple core lesion)
- Infiltrative in advanced cases
Histology:
- Adenocarcinoma is most common (95%)
- Tumor invades mucosa, submucosa, muscularis, and potentially serosa
Common Locations
| Location | Symptoms | % of Cases |
|---|---|---|
| Right-sided colon | Anemia, weight loss, mass in RIF | 20% |
| Left-sided colon | Altered bowel habits, bleeding | 30% |
| Rectum | Tenesmus, rectal bleeding, mass | 50% |
Clinical Features
- Abdominal pain (colicky or continuous)
- Change in bowel habits (diarrhea/constipation)
- Rectal bleeding or mucus in stool
- Tenesmus (feeling of incomplete evacuation)
- Unexplained anemia
- Weight loss, fatigue, and weakness
- Palpable mass (especially in rectal cancer)
Staging of Colorectal Cancer
Dukes' Staging (Traditional):
- A: Confined to bowel wall
- B: Through bowel wall
- C: Involving lymph nodes
- D: Distant metastasis
TNM Staging (Modern):
- T1–T4: Depth of invasion
- N0–N2: Number of lymph nodes involved
- M0–M1: Metastasis absent or present
NIC Staging (Integrated Clinicopathologic):
- Combines TNM with prognostic factors for therapy planning
Diagnostic Investigations
1. Digital rectal exam and fecal occult blood test (FOBT)
2. Blood tests:
- FBC (for anemia)
- Liver function tests (for liver metastasis)
- CEA (tumor marker for monitoring)
3. Endoscopy:
- Sigmoidoscopy or colonoscopy with biopsy
4. Imaging:
- Barium enema
- CT colonography (virtual colonoscopy)
- Transrectal ultrasound (TRUS)
- MRI pelvis (especially for rectal tumors)
Treatment of Colorectal Carcinoma
Surgery (Curative for Localized Disease)
| Tumor Location | Surgery Type |
|---|---|
| Right-sided colon | Right/extended right hemicolectomy |
| Left-sided colon | Left hemicolectomy/high anterior resection |
| Rectum | Anterior resection or abdominoperineal excision |
Hartmann’s Procedure:
- For emergency settings in left-sided obstruction or perforation
Adjuvant Treatments
1. Chemotherapy:- Used in Stage III/IV or node-positive cancers
- Agents: 5-FU, oxaliplatin, irinotecan
2. Radiotherapy:
- Mostly for rectal cancer
- Given pre-op to reduce tumor bulk or post-op for margins
3. Targeted therapy:
- For metastatic CRC (e.g., bevacizumab, cetuximab)
Palliative Treatments
- Tumor resection or bypass for symptom control
- Stents for obstructive lesions
- Palliative chemotherapy for unresectable tumors
2-Week Referral Criteria for Suspected CRC (NHS Guideline)
- Rectal bleeding + change in stool frequency >6 weeks
- Unexplained iron deficiency anemia
- Palpable rectal/abdominal mass
- Persistent loose stools >6 weeks
- Age >50 with rectal bleeding
Prognosis
| Stage | 5-Year Survival Rate |
|---|---|
| Stage I | 75% |
| Stage II | 55% |
| Stage III | 45% |
| Stage IV | 6% |
- Early detection dramatically improves survival
- Liver resection for isolated metastasis can improve prognosis
- Regular surveillance is vital post-treatment
Prevention and Screening
Screening Methods:
- Fecal occult blood testing (FOBT)
- Fecal immunochemical test (FIT)
- Colonoscopy every 10 years after age 50
- Flexible sigmoidoscopy every 5 years
- Genetic counseling in high-risk individuals
Lifestyle Tips:
High-fiber diet
Limit red and processed meat
Exercise regularly
Maintain healthy body weight
Avoid smoking and alcohol
Frequently Asked Questions (FAQs)
Q1. Is colorectal cancer curable?
A: Yes, if detected early. Surgery offers high cure rates in Stage I and II cancers.
Q2. What are the first signs of CRC?
A: Rectal bleeding, anemia, unexplained weight loss, and altered bowel habits.
Q3. How often should one be screened?
A: From age 50 every 10 years with colonoscopy (earlier if high risk).
Q4. Is chemotherapy always required?
A: Not in early-stage CRC. It’s typically used in node-positive or metastatic disease.
Q5. Can CRC spread to other organs?
A: Yes. Liver and lungs are common sites of metastasis.
Summary Table: Colorectal Carcinoma at a Glance
| Feature | Details |
|---|---|
| Origin | Colon or rectum mucosa |
| Symptoms | Bleeding, altered bowel habits |
| Diagnosis | Colonoscopy with biopsy |
| Treatment | Surgery, chemo, radiotherapy |
| Prognosis | Depends on stage (I–IV) |
| Risk Factors | Polyps, IBD, genetics, diet |
| Prevention | Screening, healthy lifestyle |
