Virtual Colonoscopy: Preferred Colorectal Cancer Screening Technique In Average Risk Asymptomatic Adults

1
Virtual Colonoscopy Preferred Colorectal Cancer
Screening Technique In Average Risk Asymptomatic
Adults

• By Katy Carroll
• Advisor David Fahringer
• March 8, 2007
• PAS 646

2
Why Screen?

• Best method for controlling colorectal cancer
• 70-75 of CRC occurs in asymptomatic individuals
• Detect and remove adenomatous polyps, precursor
  lesions for CRC, and detection of early stage
  carcinoma
• Reduce mortality

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Barriers to Screening

• Race
• Lack of health care coverage
• Low education levels
• Fear of pain
• Fear of complications during procedure
• Embarrassment of preparation process
• Morbidly obese adults
• Cost issues
• Lost time from work
• Lack of access
• Sex of endoscopist

4
Risk factors for CRC

• Family history of colorectal cancer
• Personal history of adenomas or ovarian/uterine
  cancer
• Long standing IBD (8-15 years)
• Environmental factors (diet and meds)
• Lifestyle factors (physical inactivity, obesity,
  and cigarette smoking)

5
Incidence Mortality

• Second most common cancer in United States
• Second leading cause of cancer related death in
  the USA

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Why Discrepancies?

• 35 of CRCs diagnosed at localized stage in
  African Americans compared to 39 in Caucasians
• Possibly due to hormone and NSAID use
• Less utilization of current screening methods

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Pathophysiology

• Current belief is that most CRCs stem from
  preexisting adenomas
• Adenomas that are large and/or have a villous
  component determine likelihood of containing
  invasive carcinoma
• Polyps are slow growing and must grow for five
  years before they are clinically significant
• Normal colonic mucosa is transformed into benign
  adenoma, followed by progression to polyp
  containing cancer, which can become invasive

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Methods for Screening

• Colonoscopy
• Flexible sigmoidoscopy
• Air contrast barium enema
• Fecal occult blood test (FOBT)
• CT colonoscopy

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Detection Rates

• Colonoscopy Sensitivity of 88.2 (gt10mm)
• Sensitivity of 90.0 (lt6mm)
• CT colonoscopy Sensitivity of 92.2 (gt10mm)
• Sensitivity of 85.7 (lt6mm)
• FOBT detected 23.9 of advanced neoplasia
• Flex Sig 76 when used with FOBT
• Air contrast barium enema failed to identify up
  to 50 of polyps greater than 10mm in diameter

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Cost

• Screening with any method is more cost effective
  than treating/intervening when compared with no
  screening

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Virtual vs. Optical Colonoscopy

• Patients reported less discomfort with virtual
  colonoscopy
• Shorter examination time with VC
• VC less embarrassing
• 72.3 of patients preferred VC as screening
  technique compared to 5 preferred CC as
  screening technique
• More patients were willing to repeat a VC at
  shorter intervals than CC

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Remove Barriers

• Study by Pickhardt et al. showed that when CT
  colonoscopy was covered by third party payers,
  patient demand for procedure rapidly increased.
• Third party reimbursement for virtual colonoscopy
  has the potential to make a significant impact on
  patient compliance with CRC screening guidelines.
• Fear of pain

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Conclusion

• Not screening for CRC has great cost measured in
  dollars and lives
• Very high detection rates in people with polyps
  over 5mm
• Low detection rates for polyps less than 5mm
  could be acceptable because majority of polyps
  this size do not progress to CRC
• Studies underway concerning technology advances
  that can affect the sensitivity and specificity
  for polyps and malignancy

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Conclusion (Cont.)

• If optical and virtual colonoscopy were covered
  equally on insurance plans more people would be
  compliant with CRC screening guidelines- as in
  Pickhardts study
• Less time for actual procedure saves screening
  sites money
• U.S. government would save money in the long run
  due to reduced Medicare/Medicaid money being
  spent on treatment/intervention
• Studies with stool tagging and digital
  subtraction are going on to eliminate bowel
  preparation, which would increase patient
  acceptance

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