Report 10 of the Council on Scientific Affairs (A-03)

Commercialized Medical Screening

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Summary

Objectives: To briefly review the use of electron beam computed tomography (CT) for determining coronary artery calcification, spiral CT for lung cancer screening, and CT colonography for colon cancer screening in the context of generally accepted criteria that comprise a valid screening test. The use of total body scans for screening purposes was not specifically evaluated.

Methods: Literature searches were conducted in the MEDLINE and Nexis databases for English-language articles published between 1990 and March 2003 using the search terms screening, mass screening, and tomography, x-ray computed or radiography, as well as the text terms electron beam computed tomography, or virtual colonoscopy, in combination with calcium, coronary angiography, coronary arteriosclerosis, coronary disease, lung, lung neoplasms, thoracic, adenocarcinoma, colon, colonoscopy, colorectal or colonic neoplasms, colonography, and colonic polyps, A total of 812 citations were identified; 272 were retrieved for analysis. Additional references were culled from the bibliographies of these references.

Results: The detection and quantification of coronary arterial calcification (CAC) serves as a sensitive surrogate marker of the total plaque burden and carries some positive and negative predictive value for estimating the likelihood of future coronary events. The degree to which CAC independently estimates the risk of coronary heart disease, or adds incremental value to established risk factors is still undetermined. Spiral CT is more sensitive than routine chest x-ray in detecting uncalcified lung nodules, allowing the possibility that more patients may be diagnosed with early stage disease. Spiral CT may prove to be a very important tool for early detection of lung cancer, but at this time, only prevalence-screening data and preliminary survival data in observational cohorts are available. CT colonography is less sensitive than conventional colonoscopy and patients with positive scans ultimately must also undergo a conventional colonoscopy. CT colonography is useful, however, in patients who refuse to undergo colonoscopy for various reasons, and in patients following failed or incomplete colonoscopy. As yet, none of these screening tests have been shown to reduce disease-specific mortality, but trials are under way to answer this question.

Conclusions: Large, prospective, multicenter trials are currently under way or in the planning phase to evaluate whether these screening examinations are clinically valid and reduce the rate of mortality. The medical profession should continue to advocate the use of clinically effective and cost-effective procedures and interventions. Relevant specialty societies can assist by continuing to evaluate the validity and clinical use of screening imaging procedures that are advertised directly to the public and make available to the broader physician community unbiased evaluations to help primary care physicians advise their patients on the risks and benefits of these procedures.

RECOMMENDATIONS

The following statements, recommended by the Council on Scientific Affairs, were adopted by the AMA House of Delegates as AMA policy and directives at the 2003 AMA Annual Meeting:

1. Relevant specialty societies should continue to evaluate the validity and clinical use of screening imaging procedures that are advertised directly to the public and make available to the broader physician community unbiased evaluations to help primary care physicians advise their patients of the risks and benefits of these procedures. (Policy)
2. The AMA will urge government funding agencies to continue to fund well-designed, large-scale clinical trials aimed at determining the safety, value, and cost-effectiveness of screening imaging procedures. (Directive)
3. Considering the summary information in this report, the Council on Ethical and Judicial Affairs will further consider the ethical ramifications of commercialized medical screening. (Directive)