Overview
Colon cancer (large bowel cancer) is cancer that begins in the large intestine. It is the 3rd most common type of cancer worldwide; about 20,000 new cases are diagnosed annually in our country. It is seen at similar rates in men and women.
Colon cancer usually starts from benign growths called polyps; over years it can turn into cancer. When diagnosed early, treatment success exceeds 90%.
Symptoms
There may be no symptoms in the early stages; therefore screening is very important.
- Change in bowel habits (diarrhea, constipation, change in stool consistency — lasting more than 4 weeks)
- Rectal bleeding, bloody stools
- Persistent abdominal discomfort (cramps, gas, pain)
- Feeling of incomplete evacuation
- Weakness, fatigue
- Unexplained weight loss
- Iron deficiency anemia
- Palpable mass in the abdomen
- Thin, pencil-like stools
- Mucousy stools
Causes
Uncontrolled multiplication due to mutations in the DNA of colon cells. Usually:
- First, a benign polyp forms (adenoma)
- Over years, it turns into cancer (adenoma-carcinoma sequence)
Risk Factors
Non-modifiable:
- Age: Over 50 (90%)
- Family history: Colon cancer in 1st degree relatives
- Personal history of polyps or cancer
- Hereditary syndromes: Lynch syndrome, Familial Adenomatous Polyposis (FAP)
- Inflammatory bowel diseases: Crohn's, ulcerative colitis
- Type 2 diabetes
- Ethnicity
Lifestyle:
- Sedentary lifestyle
- Obesity
- Diet low in fiber, high in fat and red meat
- Processed meat consumption
- Smoking
- Excessive alcohol
- Vitamin D deficiency
Complications
- Bowel obstruction
- Bowel perforation
- Acute abdomen
- Liver, lung, peritoneal, lymph node metastases
- Anemia, blood loss
- Malnutrition
- Death
Screening Recommendations
Average-risk individuals:
- Screening should begin at age 50 (45 in some guidelines)
- Methods:
- Colonoscopy: Every 10 years (gold standard)
- Fecal occult blood test (FOBT/FIT): Annual
- Sigmoidoscopy: Every 5 years
- Virtual colonoscopy (CT colonography): Every 5 years
High-risk individuals: Earlier and more frequent screening (age 40 or 10 years before the family case)
When to See a Doctor
- Change in bowel habits lasting more than 4 weeks
- Rectal bleeding, bloody stools
- Unexplained weight loss
- Persistent abdominal pain
- Weakness, anemia
- Over age 50 (screening)
- Earlier age if family history
Diagnosis and Treatment
Diagnosis:
- Colonoscopy + biopsy (definitive diagnosis)
- Computed tomography (CT): Staging
- MRI: Liver and rectal evaluation
- PET-CT: Metastasis screening
- Blood tests: Complete blood count, CEA (tumor marker)
- Genetic tests (if Lynch, FAP suspected)
Staging (TNM):
- Stage 0: Limited to mucosa (in situ)
- Stage 1-2: Limited to bowel wall
- Stage 3: Lymph node involvement
- Stage 4: Distant metastasis
Treatment (by stage):
Surgery (mainstay):
- Local excision (in polyps)
- Partial colectomy (removing the cancerous part of the colon)
- Laparoscopic or robotic surgery
- Total colectomy (in Lynch, FAP)
- Colostomy (temporary or permanent)
Chemotherapy:
- After surgery in Stage 3 (FOLFOX, CAPOX)
- Main treatment in Stage 4
- Chemotherapy drugs: 5-FU, oxaliplatin, irinotecan, capecitabine
Targeted therapy:
- Bevacizumab (anti-VEGF)
- Cetuximab, panitumumab (anti-EGFR for KRAS wild-type tumors)
Immunotherapy:
- Pembrolizumab, nivolumab (MSI-high tumors)
Radiotherapy:
- Frequently used in rectal cancer
- Pre- or post-surgery
Prevention
Screening (most effective protection):
- Colonoscopy starting at age 50
- Earlier if there is family history
- Polyps should be removed when detected
Lifestyle:
- Regular exercise (150 minutes per week)
- Maintain a healthy weight
- Plenty of vegetables, fruits, whole grains
- Limit red and processed meat (<500 g per week)
- High-fiber diet
- Quit smoking
- Limit alcohol
- Adequate vitamin D and calcium
- Regular aspirin (in some high-risk patients with doctor's advice)
Medical:
- Follow up IBD (Crohn's, ulcerative colitis)
- Inform your doctor about your family history
- Genetic counseling (when hereditary syndrome is suspected)
- Keep your diabetes under control