Screening for Colorectal Cancer
Cancer Symposium: Measuring the Benefits of Screening and
Treatment
October 2007
Why should we screen of colon and rectal cancer?
Because it is common
• Third most common cancer in Canada– 20,400 new cases
• Second most lethal– 8,700 deaths
• The most lethal among non smokers
Natural History
• The polyp cancer sequence
• Surgical and endoscopic techniques
Because we can
Screening for CRC
• No symptoms
• Average risk
• High risk
Screening for CRC
• Average risk individual– When to start?
• Age 50– Incidence 1:500 age 40 -49 y– 1:125 50-59 y– 1:50 60-69 y
Fecal Occult Blood Testing
• The only screening test with Level I evidence that it can decrease the mortality from CRC– NEJM 1993 Minnesota Trial– Lancet 1996 European Study
• 18 yr follow-up from the Minnesota Trial shows an 21% mortality reduction in the screening cohort
FOBT
• “2 samples from each of 3 consecutive stool samples, with dietary restrictions if using a guaiac based test”
• Any positive result followed up with colonoscopy
FOBT
• How often?
• High false positive rate
• Significant false negative rate
Canadian Task Force on Preventative Health
• “the number needed to screen for 10 years to avert one death from colorectal cancer is 1173”
Flexible Sigmoidoscopy: The Good
• The scope is 50 cm long– Easier– Perforation rate is low
• Most cancers (in average risk individuals) are within 50 cm
• Biopsy and polypectomy is possible
Flexible Sigmoidoscopy: The Bad
• The scope is 50 cm long
• Perforation rate is 1.4 per 1000
• Prep is necessary
Flexible Sigmoidoscopy
• Good for 5 years
• ? Should one do a full colonoscopy if a low risk polyp is found in the distal colon– Lancet 2002 UK RCT found an 80%
mortality reduction form CRC
Double Contrast Barium Enema
• No randomized trails that evaluate this as a screening tool for average risk individuals
• It does not see the rectum well
• It misses 50% of polyps < 1.0 cm
• Q 5 years
Combinations
• DCBE and Flex sig– No data
• FOBT and Flex sig– Limited data
Colonoscopy: The Good
• Although there is no evidence……
• Allows diagnostic biopsy and endoscopic removal of polyps
• Shelf life of 10 years in average risk individuals
Colonoscopy: The Bad
• Highly trained personnel
• Resource intense
• Expensive
• Do we have the capacity?
Colonoscopy: The Ugly
• Prep
• Perforation risk– 1:1000 all comers– 1:2000 screening– 1:15000 mortality
Emerging Technologies
• Fecal DNA analysis
• Virtual colonoscopy
Virtual Colonoscopy
Emerging Technologies
• Fecal DNA analysis
• Virtual colonoscopy
• Micro array gene expression analysis
High Risk Individuals
• Good news and bad news
• Family History
• FAP
• HNPCC
• IBD
Family history
• 1 first degree relative < 60 with CRC or polyp disease or
• 2 first degree relatives with CRC at any age
• Begin at age 40, or 10 years younger than the youngest relative and continue q 5 years
Family history
• 1 First degree relative > 60 with CRC or polyp disease or
• 2 second degree relatives with CRC at any age
• Should be screened as an average risk but beginning at age 40
Family History
• 1 second degree relative or any number of third degree relatives should be screened as average risk
Familial Adenomatous Polyposis (FAP)
• Flexible sigmoidoscopy at age 14
• +/- genetic testing
Hereditary Non-polyposis Colon Cancer (HNPCC)
• Amsterdam II Criteria– 3 relatives (at least I first degree)– Successive generations– One with Ca <50– FAP r/o
HNPCC
• Colonoscopy q 2 years
• +/- genetic testing for MMR gene mutation
• +/- genomic analysis of tissue for micro satellite instability
Patients with Inflammatory Bowel Disease
• Same for UC or Crohns
• 8 years after the onset of disease in pancolitis• 15 years after onset in Left sided disease
• Colonoscopy q 1 - 2 years
Patients with a history of Polyps
• Advanced adenoma– >10 mm– Villous architecture– HGD
• >2 polyps less than 10 mm
• AGA……3 years• CAG…….clinical judgment
Patients with a history of polyps
• One or two polyps , each less than or = 10 mm
• 5 years
Summary
• Screening is good• Begin at age 50 in average risk individuals• Options
– FOBT +/- colonoscopy– colonoscopy
• High risk individuals should have colonoscopy
Questions
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