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Update on Colorectal Cancer Screening Tests

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... American Cancer Society, the US Multi-Society Task Force on Colorectal Cancer, and the American ... Colorectal cancer prevention (not CRC mortality ... – PowerPoint PPT presentation

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Title: Update on Colorectal Cancer Screening Tests


1
Update on Colorectal Cancer Screening Tests
Source Levin Bernard et al. Screening and
Surveillance for the Early Detection of
Colorectal Cancer and Adenomatous Polyps, 2008
A Joint Guideline from the American Cancer
Society, the US Multi-Society Task Force on
Colorectal Cancer, and the American College of
Radiology. CA A Cancer Journal for Clinicians
58(3)130-160, May/June 2008.
2

Colorectal Cancer
Americas 2 Cancer Killer

3
Expert Panel Opinion
  • Colorectal cancer prevention (not CRC mortality
    reduction) should be primary goal of CRC
    screening.
  • Tests designed to detect both early cancer and
    adenomatous polyps should be encouraged if
    resources available and patients willing to
    undergo test.

4
Testing Options for Early Detection of Colorectal
Cancer and Adenomatous Polyps for Average-risk
Women and Men Aged 50 Years and Older
  • Partial or full structural exams (invasive tests
    that detect adenomatous polyps and cancer)
  • Flexible sigmoidoscopy every 5 years
  • Colonoscopy every 10 years
  • Double-contrast barium enema every 5 years
  • Computed tomographic colonography every 5 years
  • Fecal tests with high test sensitivity
    (noninvasive tests that primarily detect cancer)
  • Annual guaiac-based fecal occult test (gFOBT)
  • Annual fecal immunochemical test (FIT)
  • Stool DNA test

Note Expert panel does NOT recommend gFOBT
testing in doctors office as a single-panel
test following digital rectal exam.
5
Limitations and Requirements of Fecal Tests
  • Less likely to prevent cancer compared with
    invasive tests
  • Must be repeated at regular intervals to be
    effective
  • If abnormal, an invasive test (colonoscopy) will
    be needed

6
Stool DNA TestNew Recommended Test
7
Colorectal cancerA series of genetic defects
5q(APC) alterations
K-RAS mutation
17p (p53) alterations
18q alterations
Carcinoma
Advanced Adenoma
Normal
Adenoma

Colonic epithelium
Benign neoplasia
Larger Tumor
Malignant neoplasia
8
Stool DNA Test
  • Prototype assay of this test (version 1.0)
  • 23 DNA markers assayed
  • 21 point mutations in K-ras, APC, and p53
  • 1 microsatellite instability marker BAT-26
  • DNA Integrity Assay (DIA)
  • Minimum 30 grams of stool required
  • Specific for human DNA - diet not needed
  • Currently available assay (version 1.1)
  • Same DNA marker panel
  • Incorporates technical advances in processing and
    specimen preservation to increase test sensitivity

9
Stool DNA Screening Process
Physician
Stool DNA Analysis Is Performed in Lab and
Reported to
Patient Collects
Sends
Stool at Home
Requisition
to Lab
Physician
Ice Pack
Lab Provides
Patient Returns
Physician Communicates Results to Patient
Collection and
Specimen to Lab
DNA Alteration Identified Perform colonoscopy
Shipping Materials
to Patient

No DNA Alteration Identified Continue screening
10
Stool DNA Test
  • Pros
  • Noninvasive, private
  • No dietary restriction or cathartics
  • One specimen no need to handle stool
  • Acceptable sensitivity
  • High acceptance by patient and provider
  • Detects other cancers
  • Cons
  • Sensitivity less than colonoscopy
  • Cost high relative to FIT or gFOBT
  • Performance intervals unknown
  • Cost-effectiveness needs further study
  • Panel of markers identifies majority, but not
    all, of CRC
  • Significance of positive test result in patient
    with negative follow-up evaluation unknown

11
Stool DNA TestKey Issues for Informed Patient
Decisions
  • Adequate stool sample must be obtained and
    packaged with appropriate preservative agents in
    shipping to laboratory
  • Unit cost of currently available test
    significantly higher than other forms of stool
    testing (e.g., 575 DNAdirect Genetic Testing
    Online)
  • If test positive, colonoscopy recommended
  • If test negative, appropriate interval for repeat
    test uncertain (manufacturer recommending 5-year
    interval)

12
Virtual Colonoscopy or CTC (Computed Tomographic
Colonography)New Recommended Test
  • Minimally invasive CT imaging examination of the
    entire colon and rectum
  • Adequate bowel prep and gaseous distention of
    colorectum essential to quality exam
  • Uses advanced 2-dimensional and 3-dimensional
    image display techniques for interpretation
  • Since introduction in mid-1990s, rapid
    advancements in CTC technology have occurred

13
CT-scanner for Virtual Colonography
Colonoscopy View
Virtual Colonography View
14
Virtual Colonoscopy or CTC
  • Pros
  • Time-efficient procedure
  • Good accuracy
  • Minimal invasiveness
  • No sedation or recovery time
  • Patient can return to work same day
  • Potential for same day colonoscopy
  • Detection of non-GI abnormalities
  • Cons
  • Reimbursement for screening CTC currently limited
  • Professional capacity to deliver limited
  • Requires bowel prep
  • Quality of interpretation highly operator
    dependent
  • Controversy over radiation dose effects
  • Relatively expensive (400 - 800)

15
Virtual Colonoscopy or CTCKey Issues for
Informed Patient Decisions
  • Complete bowel prep required
  • If patient has one or more polyps 6 mm,
    colonoscopy recommended if same day colonoscopy
    not available, second complete bowel prep
    required
  • Risks are low rare cases of perforation reported
  • Extracolonic abnormalities may be identified

16
Summary
  • Colorectal Cancer Screening Report
  • from Expert Panel
  • Promote colorectal cancer prevention as primary
    goal
  • Endorses two new screening tests Stool DNA and
    CTC
  • Recommends fecal tests with high test sensitivity
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