165. Colorectal Cancer

Question 1

Epidemiology: trends over time, race

risk factors for CRC

Pathogenesis of CRC

Answer 1

Incidence/mortality rates decreased over time (screening, early detection, more effective tx), but increased in mortality/incidence in those younger than 50 (enviro?)
Higher incidence/mortality in blacks/native americans than whites

RF:

• age (90% after age 50)
• diet/enviro (high fat/low fiber, obesity, DM, cholecytectomy, red meat, radiation)
• FamHx (FAP - APC - tx subtotal colectomy, hundreds of polyps, Lynch/HNPCC - MMR, no polyps, tumors from flat adenomas, tx: subtotal colectomy) - need for earlier screening
• IBD (longstanding UC, pancolitis)
• prior hx of cancer/polyps

Adenoma to Carcinoma path
Mutations germline for syndromes; somatic for sporadic
Normal - Dysplastic - Early adenoma - Late Adenoma - Carcinoma - Metastatic Carcinoma pathway

Question 2

Sx and signs of CRC - how does location of tumor matter?

What is the staging for CRC tumors?

Answer 2

L colon: obstructive sx: change in bowel movement pattern, pain, hematochezia
R Colon: chronic blood loss, fatigue, anemia of Fe deficiency
Rectum: local pain

I/II: invades various depths
III: +LN involvement
IV: metastases

Question 3

Treatment of CRC

Answer 3

SURGERY: clear margins, may have permanent colostomy, resect liver/lung mets too
Chemotherapy: adjuvant for tumors with high risk of recurrence (Stage III colon, Stage II/III rectal) - to eradicate micrometastases
Radiotherapy: Stage II/III rectal cancer
Palliative Care: to tx obstruction, delay progression, pain management
Colon Stage I, II = surgery, III = chemo, IV = surgery, chemo, radiation, resect mets
Rectal Stage I = surgery, II/III = surgery, chemo, radio, IV = surgery, chemo, radio, resect mets

Question 4

Screening tests for CRC

Answer 4

1. FOBT (FIT): large polyps may also bleed, false positives, need to repeat yearly/every three years for FIT-DNA, if positive test - need colonoscopy
2. Flexible sigmoidoscopy: only detect distal polyps, repeat at 5 years, need colonoscopy if polyps/cancer detected
3. Colonoscopy: can biopsy/remove lesions, higher cost, need to sedate, repeat every 10 yrs if negative
4. CT colonography: no biopsy allowed, unclear impact/risks
5. Capsule colonoscopy: swallow camera, need colonoscopy if see abnormal

Blacks start age 45, everyone else age 50
Colonoscopy every 10 years or annual FIT
+FamHx <60yo: screen at 40 (or 10 years before dx) and repeat every 5 years
+FamHx >60yo: screen at 40 and repeat every 10 years
Hx of Polyps/CRC: specific guidelines
IBD: colonoscopy every 1-2 years
FAP: endoscopy screenings in teens
Lynch: colonoscopy at 20-25, repeat 1-2yrs

Stop screening at 75 yrs with negative results, life expectancy less than 10 years, 85+ without prior screening