Colon cancer

A large proportion of colon cancers come from premalignant lesions (polyps) over multiple years (~10 years). A number of factors can increase the risk of developing colon cancer through this pathology:

• Age >50 years 
• ETOH 
• Smoking 
• Obesity
• Processed red meats

The rest of the cancerous lesions are due to inflammation (Crohn's or Ulcerative Colitis) and genetics.

• The first step is medical therapy 
• Some people fail medical therapy 
• Types 
  • 
  • Crohn's disease
    • 
    • Transmural coverage - can form fistulas 
    • Signs 
      • Fecal soiling present 
    • Diagnosis 
    • Treatment
      • Medical management only unless there is a fistula 
      • Fistulatomy  
  • Ulcerative colitis 
    • Affects the superficial mucosa of the colon 
    • Continuous inflammation starting from the rectum - no skip lesions 
    • Signs 
      • Bloody bowel movements - will require a colonoscopy 
      • Rectal pain 
      • Weight loss 
    • Treatment 
      • Medical until 8 years 
        • 8 years after diagnosis = screening colonoscopy every year due to increased cancer risk 
        • Prophylactic colectomy will cure the disease 

The most known genetic causes of bowel cancer are familial adenomatous polyposis (FAP) and Lynch syndrome. Below those and a few more genetic causes of colon cancer are discussed. 

• FAP 
  • Pathophysiology
    • Defect in the APC gene 
    • 1000s of polyps at a young age (in their 20s)
      • 
    • These patients get colon cancer in their 30s and pass away by their 40s
  • Prevention
    • Prophylactic colectomy
    • Early screening at age 10-15
• Lynch syndrome - also known as hereditary non polyposis colorectal cancer (HNPCC)
  • Pathophysiology 
    • Defect in the DNA mismatch repair systems
    • No polyps involved, but will still get colorectal cancer
    • Often multiple members of the family affected
      • Remember the 3-2-1 rule 
        • 3 cancers (colon, endometrial or ovarian) in 2 generations and at least 1 premature age = Likely to be Lynch syndrome
    • Additionally these patients will also get 
      • Colon cancers
      • Endmetrial cancers
      • Ovarian cancers
• Turcot's - (Remember: "turban" = head tumours)
  • Pathophysiology 
    • Brain tumours and colon cancer 
• Gardner's 
  • Pathophysiology 
    • Jaw tumours and colon cancer
• Peutz Jegherr
  • Presentation - Freckles around the mouth
    • 
  • Pathophysiology
    • No colon cancer is present 
    • Small bowel cancer 
    • Will have to do endoscopy instead of colonoscopy

Presentation 

• 3 common ways of presentation for most colon cancers are the followings: 
  1. Found on an asymptomatic screen
     • Regular screening age 
       • Age 50-75 (or 85 depending on the patient's mortality risk)
     • Good polyps
       • Pedunculated 
       • Tubular 
       • Small size
     • Bad polyps
       • Sessile
       • Villous 
       • Large size  
     • Polyps in detail 

       • Inflammatory	Common in patients with IBD	Low cancer risk	Remove during colonoscopy
         Hyperplastic	Small and located terminal to the colon	Low cancer risk	Remove during colonoscopy
         Tubular adenoma	70% of polyps are these	Low risk if small in size	Remove during colonoscopy Increased follow up frequency required
         Villous	15% of polyps are these	Higher risk, especially if big in size	Remove during colonoscopy Larger polyps may require surgery
         Serrated adenoma	The remaining 10-15% of polyps are these	Lead to 20-30% of the colon cancer cases	Hard to see and remove with colonoscopy

  2. Iron deficiency anemia 
     • Concerning in men and post menopausal women 
  3. Pencil thin stool or other signs of a mass
     • 
     • Can have altered bowel habits (constipation and diarrhea) 
     • Can progress into a full obstruction Will have to do a colonoscopy with a biopsy 

Diagnosis 

• Colonoscopy with a biopsy
  • 
  • Regular screening ages are 50-75 
  • After age 75, have to calculate the risks and benefits to the individual patient
  • If nothing is found
    • No risk
    • Repeat every 10 years  
  • If a polyp is found 
    • Low risk
      • 1-2 polyps, all of which are tubular with low grade dysplasia and <1cm in size
      • Repeat every 5 years  
    • High risk 
      • >3 polyps or >1cm or villous type or high grade dysplasia 
      • Repeat every 1-3 years 
    • Mega risk 
      • >10 polyps 
      • Piecemeal sessile polyp present 
      • Repeat within 2-6 months
• Flexible sigmoidoscopy 
  • Ages 50-75 
  • Repeat every 5 years if nothing found
  • Must be done with fetal occult blood testing (FOBT) every 3 years or every year
• FIT testing 
  • Better than FOBT 
• CT colonography
  • Less invasive but not as good as a colonoscopy screen
• Barium enema 
  • "Apple core" picture 
  • Not used very commonly anymore 
• Staging of a confirmed cancer
  • Pan CT - CT chest, abdo and pelvis 

Treatment 

• Resection 
  • 
• Chemotherapy 
  • FOLFOX or FOLFIRI