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