7. CRC: Epidemiology/risk factors
CRC
Epidemiology
Sporadic average risk Hereditary CRC
Most common GIT cancer syndromes:
3rd most common cancer Higher than average
2nd most common cancer
CRC risk &include:
death
2% die from this cancer. FAP
Men>women AFAP
Blacks>white HNPCC
Increase sharply after 50 IBD
Familial CRC.
8.
9. Stratification of Colorectal Cancer Risk
CRC Risk
High risk
Average risk
-ve family • FAP 100%
•HNPCC 10%
history
•IBD 10-20%
Most
•Familial FDR 10%
LTR 5-6% Occur earlier <50
>50 years. minority years.
Text
ALL
10. Risk/protective factors for CRC
Risk factors protective factors
Hereditary CRC No family H/O CRC
IBD CRC Asia/Africa
WESTERN High veg;fruits/
calcium/folate
Physical inactivity
Physical activity
High red meat,
sucrose,fat
Low calcium/folate.
Obesity,smoking,
Alcohol,
cholecystectomy
13. Rationale for screening by colonoscopy
CRC
LAP with dysplasia
Screening for
early detection
Large adenomatous polyps
Small adenomatous polyps
Normal
30-50% of adults develop adenomatous polyps during their lifetime, but only 1 / 20
will progress to cancer.
15-25% >50 ys have adenomatous polyps, males>females.
14. Hereditary CRC Syndromes: FAP
Mutation in APC genes
100% will develop 100s of
adenomatous colonic polyps & cancer FAP
By 40 years age.
GIT Extra colonic tumors:
2nd most common after colonic;
adenoma/adenocan of ampulla of vater,
Fundal gland polyps.
15. Hereditary CRC Syndromes: FAP
Need screening colonoscopy earlier than
The usual age of 50 years
Extra GIT Features:
Bone/soft tissue tumors FAP
Retinal pigment epith hypertrophy
Treatment:
Total colectomy with ileostomy to
prevent cancer.
16. Hereditary CRC Syndromes: AFAP
Mutations at the terminal end of
the APC gene
20 or more adenoma AFAP
SAME RISK OF CRC.
17. Hereditary CRC Syndromes: HNPCC
Mutations at DNA MMR gene
Polyps larger
more in proximal colon HNPCC
Progress more rapidly to CRC.
8O% develop cancer >50
Vs 5% > 50 in average risk persons.
Extra-colonic tumors:FRS,Kid,pancbil,SI
18. Hereditary CRC Syndromes: familial
Do not meet criteria for FAP or HNPCC
1ST degree or 2nd degree relative with
CRC before or after 50 Familal CRC
Risk increase with increasing numbers of
Affected relatives.
19. Hereditary CRC Syndromes: others
Familial juvenile polyposis
the Peutz-Jeghers syndrome
(hamartomatous polyps) others
Both at increased risk for developing CRC.
20. IBD CRC risk
Duration > 8 years of active colitis
Early age of onset
Extent IBD CRC Risk
Presence of PSC.
23. Management
Surgery is the only hope for cure.
Carcinomas within 2 cm of the anal verge may require abdomin-
operineal resection & colostomy.
Postoperative colonoscopy after 6–12 months &periodically
thereafter for local recurrence or new ‘metachronous’ lesions,
occuring in 6% of cases.
Adjuvant radio-chemotherapy for rectal cancer.
Paliative chemo-radiotherapy or stenting for inoperable cases.
