Colorectal Cancer Screening

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Colorectal Cancer Screening

• September 10, 2002
• Jorge Garcia, MD

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What is the risk of getting colon cancer?

• Increases steadily with age.
• At age 50, annual risk is one in 10,000.
• At age 50, lifetime risk is one in 20. Half of
  these will of die of the cancer.
• On average, colon cancer decreases the life
  expectancy of the victim by 13 years.

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What are the more common ways if dying?

• Among 50 year old women...

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What are the more common ways if dying?

• Among 50 year old women
• 1 in 200 will get breast cancer in 10 years.
• 1 in 500 will get colon cancer in 10 years.
• 1 in 500 will die of heart disease in 10 years.
• 1 in 500 will die of an accident in 10 years.

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What are the more common ways if dying?

• Among 50 year old women
• if she smokes

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What are the more common ways if dying?

• Among 50 year old women
• if she smokes
• One in 50 will die of lung cancer in ten years.
• One in 77 will die of heart disease.

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What can prevent colon cancer?

• High fiber diet?

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What can prevent colon cancer?

• High fiber diet? Observational studies suggested
  this might help.
• Two recent randomized studies showed no benefit
  in patients with prior adenomas.

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What can prevent colon cancer?

• Calcium?

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Calcium, 1200 mg /day

• Two recent RCT in patients with prior adenomas.
• Both demonstrated reduced risk of recurrence.
• NNT 15 over four years to prevent one adenoma.

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What can prevent colon cancer?

• ?

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What can prevent colon cancer?

• NSAIDs (including COX-2 inhibitors)
• Studies only in familial polyposis.
• Reduced incidence of polyps only while on the
  medication.
• Unable to generalize to average risk patients.

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What causes colon cancer in most people?

• ?

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What causes colon cancer in most people?

• Polyps

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What causes cancer in most people?

• Adenomatous polyps are the problem

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What causes cancer in most people?

• Adenomatous polyps are the problem
• and the solution?

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Adenomatous Polyps

• Cause 80 of CRC.
• They grow slowly, undergo malignant
  transformation.
• Over a ten year period?
• Or less?

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Adenomatous Polyps

• Frequency of polyps increase with age
• At age 50, 20 of people will have at least one
  polyp.
• At age 60, 40.
• At age 80, 55.
• Most polyps are small 85 are

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Big polyps are bad.

• If years.
• If 1 cm
• 10 will become malignant in 10 years.
• 25 will become malignant in 20 years.

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Polyps are the solution.

• If they cause most cancers, finding and
  deleting them might reduce CRC mortality.

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How do you find these polyps in time?

• ...

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How do you find these polyps in time?

• FOBT
• Flexible Sigmoidoscopy
• Colonoscopy
• Barium enema
• Virtual colonoscopy

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FOBT

• Multiple randomized control trials demonstrate
  reduced mortality from CRC.
• Minnesota Colon Cancer Control Study (Mandel
  1999, Mandel 2000) showed decreased CRC mortality
  of 21-33.
• Total mortality in controls 14/1000.
• Total mortality in annual screened 9.5/1000

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FOBT

• Compliance varies from 50-75.
• Number needed to invite to screening to prevent
  one colon cancer 142.
• Total increase in life expectancy of screened
  population 6 days.

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PAP Smears

• Increase life expectancy in screened populations
  by 11.6 to 32.4 days
• and PSA decrease life expectancy in screened
  populations by one day.

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FOBT

• Rehydrating slides increase sensitivity (40 goes
  to 60),
• But decreases specificity (97 goes to 90).

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FOBT

• Annual screening increases yield of positives.
• Multiple slides increase yield.
• No evidence around changing diet or meds.

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What does a positive FOBT mean for the patient?

• ...

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What does a positive FOBT mean for the patient?

• 8 of these will have a large polyp or cancer.
• 2 will be cancer.
• Annual FOBT screening will find 50 of cancers.
• Annual FOBT will result in 38 of screened people
  being positive and needing colonoscopy.

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What about a DRE?

• ?

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What about a DRE?

• NO evidence that DREs reliably screen for CRC.
• Guiac of stool after DRE is not recommended as a
  screen for cancer.

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Flexible Sigmoidoscopy

• No randomized control studies on Flex Sigs alone.
• Case-control study (Selby) suggest that screened
  populations have fewer fatal colon cancers that
  controls.
• Flex sig alone would miss proximal cancers what
  about combining this with FOBT?

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FOBT Flex Sig

• Two recent good randomized controlled trials. One
  cohort study
• Various numbers and protocols, but
• 42 will get colonoscopy in 10 years.
• Decreased CRC mortality by 45.6.
• Increased life expectancy for screened population
  estimated to be 8.5 days (based on 50
  compliance).

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Lieberman, NEJM, July 2001

• 2885 patients
• rehydrated FOBT and colonoscopy
• 1st 60 cm was used as proxy for Flex Sig.
• Found that FOBT Flex sig would have missed 24
  of advanced adenomas (1cm).

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Lieberman, NEJM, July 2001

• Raised serious questions about the validity of
  flex sig screening.
• But his study was only a single year of FOBT.
  Would annual tests have reduced the number of
  missed adenomas?
• Not a screening population, but recruited from
  families with CRC history.

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Colonoscopy

• Medicare started paying for screening
  colonoscopies this year.

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Colonoscopy

• No randomized controlled trials of screening.
• A single case-control study suggested lower CRC
  mortality (odds ratio 0.42).
• Several strategies proposed once in a life time,
  twice in a life time, every ten years.

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Double Contrast BE

• No randomized controlled trials.
• National Polyp Study, only 48 of polyps greater
  that 1cm were found.
• Specificity also low, at 85.

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Virtual Colonoscopy

• CT Colography
• Complete bowel prep, same as with colonoscopy.
• Fill colon with air through a rectal tube.
• After the CT, perform post image processing and
  review by radiologist.
• Experimental.
• Cant see flat polyps or lesions.

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Harms of screening

• False positives from FOBT and Flex Sigs
• anxiety
• cost
• loss of time due to work up
• complications of colonoscopy...

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Harms of screening

• Sigmoidoscopy Bowel perf 1/10,000.
• Colonoscopy Conscious sedation risk?
• Published complication rate of colonoscopy
• Bleed requiring hospitalization 1/500
• Perforation 1/750
• Serious morbidity (CVA, etc.) 1/800
• Die 1/8000

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USPSTF recommendations

• Begin screening for CRC at age 50.
• Periodic FOBT (good evidence)
• Flex sig ( fair evidence)
• No evidence (yet?) for screening colonoscopy.

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My recommendation

• Annual rehydrated FOBT age 50 - 70
• Flex sig q 5 years if FOBT negative.
• Refer any hemoccult and any polyp on FS to
  colonoscopy.
• Consider primary colonoscopy at age 50 and 60 if
  sedation would be useful, and if unable to comply
  with FOBT.

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High Risk Populations the other 20 of colon
cancers...

• Family Hx of CRC
• One 1st degree relative with Dx at age
• 2 or more 1st degree relative at any age.
• May have hereditary non-polyposis colon cancer
  syndrome.

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High risk patients

• Known family or personal history of adenomatous
  polyposis.
• Ulcerative colitis present for 8 years.
• Crohns disease.
• Prior colon cancer or adenomatous polyp.

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High risk patient management

• Consult GI
• Consider colonoscopy at frequent interval, at
  least q 5 years.