Assign 1: Colorectal Cancer Flashcards
How common is mortality r/t colorectal cancer in Canada?
How is this trend changing?
Second leading cause of cancer mortality in Canada
Death rates are declining since 1980’s due to decreased cases, early diagnosis and improved treatments
How does age relate to incidence of CC?
Incidence increases with age. 90% of cases are people > 50 years.
Et of CC?
Risk factors
- Cause largely unknown Risk factors: - family hx - Crohn’s & ulcerative colitis, - familial adenomatous polyposis of the colon (mutation on chrom 5) --> will develop into carcinoma of colon if not treated - Diet - -
How is diet risk factor for colorectal cancer?
fats, sugars
High fat = inc the synthesis of bile acids in the liver, which may be converted to potential carcinogens by the bacterial flora in the colon.
Proliferation of these bact enhanced by a high refined sugar.
How is aspirin thought to provide protective measure against CC?
Aspirin may protect against colorectal cancer
- Mechanism not understood but may be to do with:
affects synthesis of prostaglandins which may influence cell proliferation of tumour growth.
Aspirin inhibits cyclooxygenase (enzyme catalyzes arachidonic acid in cell membranes –> prostaglandin)
one form of cyclooxygenase, COX-2 promotes inflammation and cell proliferation and colorectal cancers often overexpress his enzyme.
What aspects of nutrition are thought to have protective measures against CC?
Dietary fiber increases stool bulk and dilutes and removes potential carcinogens.
Vit A, C, and E thought to have protective measures
Supplemental folate and calcium, and menopausal hormone replacement therapy (estrogen) has been proposed as potential chemoprotective agents.
How many stages are seen in CC?
How is prognosis and staging usually determined?
IV
Prognosis depends largely on the extent of bowel involvement and o the presence of metastasis at the time of diagnosis. Commonly classified into TNM stages.
Describe stages I and II of CC?
including prognosis
• Stage I - tumour limited to invasion of the mucosal and submucosal layers of the colon
- has a 5 year survival rate of 90-100%
• Stage II (lymph node-negative) - tumour infiltrates into, but not through, the muscularis externa and has a 5 year survival rate of 80%
Stages III and IV of CC?
include prognosis
Stage III (lymph node-positive) tumour - tumour invasion of the serosal layer and regional lymph node involvement - 5 year survival rate is 30-50%.
• Stage IV (metastatic) tumors penetrate the serosa or adjacent organs and have a poor prognosis.
Manifestations of CC?
Cancer of the colon is present for a while before it produces symptoms.
- Bleeding is a highly significant early symptom
- change in bowel habits, diarrhea, constipation, and a sense of urgency or incomplete emptying of the bowel.
- Pain is usually a late symptom.
screening and diagnosis of CC?
1) digital rectal exam
- find neoplasms of rectum
2) occult blood tests
- Part of routine health exam, very important for detection
- if positive will follow up with other tests
3) x-ray (with barium enema)
4) sigmoidoscopy
- Simple, no sedation needed
- Examine rectum and sigmoid colon
- 40% of cases out of reach of this device (which is why fecal occult blood test so important)
and
5) colonoscopy
- Used for screening those at high risk
- View of entire colon
- More complex
- Can take biopsy
- Expensive, time consuming
Most important prognostic indicator for CC?
extent and stage of the tumour (TNM).
Tx of CC?
- only recognized treatment for is surgical removal.
- Preoperative radiation may be used and has demonstrated increased 5 year survival rates.
- Postoperative adjuvant chemotherapy may be used
- Radiation and chemo are used as palliative treatment methods.
