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