Economic Models of Colorectal Cancer Screening in Average-Risk Adults Workshop Summary (2005) / Chapter Skim
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Appendix J Recent Findings on Test Performance--Brian P. Mulhall, M.D., M.P.H.
Appendix J Recent Findings on Test Performance--Brian P. Mulhall, M.D., M.P.H.
Pages 154-188
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From page 154... ...
SLIDE 1 SLIDE 1 NOTES: I was asked to cover recent evidence on test performance for all the major colorectal cancer screening tests. I tried to take a meta-analytic approach to every test I examined, but was frustrated by the quality, quantity and heterogeneity of the various studies examining each individual test.
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From page 155... ...
These are to some extent viewed by both clinicians and the public as part of the past. Flexible sigmoidoscopy and, more importantly, colonoscopy, are where clinicians and the public currently see the state-of-the-art for colorectal cancer screening.
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From page 156... ...
. There are over a half-dozen different tests that are GUAIAC-based and even more that have been developed using immunochemical assays to address some of the limitations of GUAIAC-based stool studies Fecal occult blood tests can also be immunological ( e.g., HemoQuant)
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From page 157... ...
. Results differ based on the design of the study, number of tests used, method of follow-up and the cut-off used for positive results, for example, all adenomas, adenomas > 1 cm or actual colorectal cancer (Brevinge et al., 1997; Favennec, 1992; Gopalswamy et al., 1994; Greenberg et al., 2000; Hope et al., 1996; Kewenter et al., 1988; Ko et al., 2003; Niv et al., 1995; Rockey et al., 1998; Rosen et all., 1997; Sung et al., 2003)
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From page 158... ...
Reported specificity for CRC is generally greater than 95 percent. Based on the review of the literature, there is also no clearly superior IFOBT at present time, but it does appear to have improved performance characteristics compared to GUAIC-based FOBTs in a number of studies.
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Dr. Ko's study showed that the overall Positive Predictive Value (PPV)
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. Though no study has been done in a truly asymptomatic, average-risk screening population, the studies that have examined patients undergoing surveillance for polyps or in those with positive findings on previous studies have demonstrated a sensitivity of 30-81 percent, varying greatly depending on the size threshold used for detection of polyps (Steine et al., 1993; Saito et al., 1989; Brewster et al., 1994)
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From page 161... ...
Nonetheless, the studies cited suggest acceptable sensitivity and specificity that make the inadequate study of, and under-utilization of, this screening modality perplexing. In summary, I would suggest that the sensitivity of the DCBE is somewhere in the 50-70 percent range for polyps, and perhaps higher than that for cancer.
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162 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 8 SLIDE 8 NOTES: Flexible Sigmoidoscopy: This test has long been used for CRC screening, but has obvious limitations based on the length of insertion of the traditional Flexible Sigmoidoscopy (FlexSig) endoscope.
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From page 163... ...
However, using radiographic methods and segmentally unblinded colonoscopy, we can estimate that the specificity of colonoscopy is in the range of 90-98 percent. Use of chromoendoscopy may improve performance characteristics of colonoscopy (Eisen et al., 2002; Kiesslich et al., 2001; Lee et al., 2003; Tsuda et al., 2002)
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Those colonocytes have a representative genetic signature, and may manifest some of these abnormalities. The observation of this process has led to studies attempting to isolate either individual or combined sets of tumor markers from stool in order to define the risk of colorectal cancer in populations.
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. One recent study used a multi-target assay in order to assess test characteristics in patients with advanced neoplasia, and showed this assay had sensitivities of 64 percent and 57 percent for cancers and advanced adenomas, respectively (Tagore et al., 2003)
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L-DNA = "Long" DNA or High Molecular Weight DNA. SLIDE 12 SLIDE 12 NOTES: Virtual colonoscopy is the latest technology to receive high visibility in the press.
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of contrast materials to enhance the image. Most of the studies reported on VC procedures using typical optical colonoscopy preparations of either air or CO2 insufflation.
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Specificity for intermediate-sized polyps has been 85-95 percent, and specificity for large polyps has been about 95 percent. The positive predictive value ranged from 60 to 90 percent, and the negative predictive value in general has been between 95 and 99 percent.
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From page 169... ...
Optical colonoscopy was performed in a standard manner by 17 endoscopists, but as one of the endoscopists in the trial I am aware that the skill level varied among the 17. This study also had a stringent set of criteria for exclusion of individuals from randomization, most notably if they had a history of previous colonic studies or of any signs of cancer or polyps.
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170 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 16 SLIDE 16 NOTES: No notes.
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The reference standard for a true positive was the segmentally unblinded optical colonoscopy result.
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172 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 18 SLIDE 18 NOTES: No notes.
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APPENDIX J 173 SLIDE 19 SLIDE 19 NOTES: To summarize comparative test performance, VC found 55 polyps not seen on OC, and 21 of those were tubular adenomas greater than 6 mm. The sensitivity for advanced neoplasia was 91.5 percent for VC and 88 percent for colonoscopy.
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174 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 20 SLIDE 20 NOTES: The additional outcome measures described in this slide extracolonic findings, procedural time, and patient satisfaction are secondary outcomes that may be important in evaluating the cost-effectiveness of this technology.
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From page 175... ...
APPENDIX J 175 SLIDE 21 SLIDE 21 NOTES: Overall summary statistics for VC performance -- with a cutoff range of 8 mm or greater, sensitivity and specificity of VC are greater than 90 percent. However, test positivity rates are high, which implies that 1 in 6 patients would be referred for optical colonoscopy.
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176 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 22 SLIDE 22 NOTES: No notes.
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FDGs take up metabolically active cells. In a recently published study (Drenth, et al., 2001)
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178 ECONOMIC MODELS OF COLORECTAL CANCER SCREENING SLIDE 24 SLIDE 24 NOTES: This table shows the broad range of sensitivity and specificity for polyps and cancer across all of the technologies reviewed here.
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APPENDIX J 179 SLIDE 25 SLIDE 25 NOTES: No notes.
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From page 180... ...
FOBTs and IFOBTs have a wide range of sensitivity, but even at low sensitivity, they have demonstrated a benefit in reducing colorectal cancer. Although barium enema has acceptable sensitivity and specificity, it is in my opinion a technology on the wane, with fewer people trained to perform the procedure.
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and O Kronborg, Acceptability and compliance in screening for colorectal cancer with fecal occult blood test.
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Kewenter, Screening for colorectal neoplasia with faecal occult blood testing compared with flexible sigmoidoscopy directly in a 55-56 years' old population. Int J Colorectal Dis, 1997.
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Okubo, Estimation of the optimal cut off point in a new immunological faecal occult blood test in a corporate colorectal cancer screening programme. J Med Screen, 1996.
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Ahren, Screening and rescreening for colorectal cancer. A controlled trial of fecal occult blood testing in 27,700 subjects.
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Houghton, Fecal occult blood testing in a noncompliant inner city minority population: increased compliance and adherence to screening procedures without loss of test sensitivity using stool obtained at the time of in- office rectal examination. Am J Gastroenterol, 2001.
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Knaani, and Z Samuel, Performance characteristics and comparison of two immunochemical and two guaiac fecal occult blood screening tests for colorectal neoplasia.
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Northover, Population based randomized study of uptake and yield of screening by flexible sigmoidoscopy compared with screening by faecal occult blood testing.
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Yuen, and B.C. Wong, Evaluation of an automated immunochemical fecal occult blood test for colorectal neoplasia detection in a Chinese population.
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