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Letters to the Editor |
Department of Radiology, Beth Israel Deaconess Medical Center, 330 Brookline Avenue, Boston, MA 02215
e-mail: fhall{at}bidmc.harvard.edu
In their article in the November 2005 issue of Radiology, Dr Furtado and colleagues (1) conclude that with whole-body computed tomographic (CT) screening "37% of patients had findings that elicited recommendations for additional evaluation," usually callback imaging examinations, "but further research is required to determine the clinical importance of these findings and the effect on patient care." In the same issue, Dr MacMahon and colleagues (2), in a statement from the Fleischner Society, provide guidelines for the follow-up and management of small nodules detected at CT in low-risk and high-risk individuals. These two important articles provide provisional data that will help to form a more rational basis for whole-body CT screening.
The decision of whether to further evaluate or follow-up incidentally noted abnormalities seen with diagnostic imaging examinations, particularly the myriad of serendipitous findings seen with CT, is difficult. These decisions are the crux of screening studies. When there are objective criteria, such as size, or known pretest probabilities, such as age, then guidelines can be developed by groups of experts, such as the Fleischner Society has done for small pulmonary nodules (2). However, when the abnormalities are more subjective, we need consensus guidelines such as an acceptable percentage of callback and/or follow-up cases. As detailed by Dr Furtado and colleagues (1), these guidelines might be applicable to the entire whole-body CT examination, as well as to individual organ systems, and would differ depending on, for example, the use of intravenously administered contrast media.
Many of the difficult lessons learned from screening mammography are applicable to whole-body CT and other screening examinations. For example, mammographers in the United States have established a "standard" of less than 10% for the number of screening callback or follow-up cases. The number is slightly lower in most European countries, perhaps due to more dedicated and/or experienced readers and diminished medicolegal concerns. Callback rates are easily ascertained for both individuals and groups, and in the United States the collection of these data are legally mandated.
The 37% recommendation for additional evaluation in whole-body CT screening found by Dr Furtado and colleagues (1) seems to me to be far too high to make this examination cost-effective. When mammography screening began, the callback rate for additional imaging was frequently more than 20%, which is twice the current acceptable rate. I suspect whole-body CT screening will undergo similar reductions, with gradual acceptance of a slight decrease in sensitivity in order to decrease false-positive findings. Disease-specific survival or general survival, the reference standards for effective screening, will come much later and, if the history of screening mammography is any indication, they will be controversial.
I believe that whole-body CT screening will find an appropriate small niche in medicine, at least in the United States and other more affluent countries where $50 000 per quality life year saved is commonly the cutoff for cost-effective medical tests and interventions. However, I also strongly believe that whole-body CT screening is best performed on non-worrying patients who have practical non-worrying physicians and that the examinations are best interpreted by non-worrying radiologists. Unfortunately, a disproportionate number of patients who currently seek out screening CT examinations are "worriers," and too many physician recommendations are motivated by medicolegal concerns. In my opinion, callback guidelines or standards will be very helpful in this regard, as they have been in breast screening. Those mammographers who cannot meet these guidelines should not be interpreting screening mammography studies. As Harry Truman so pithily put it: "If you can't take the heat then get out of the kitchen."
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Department of Radiology, University of California San Diego, 200 West Arbor Drive, San Diego, CA 92103-8756
e-mail: gcasola{at}ucsd.edu
We thank Dr Hall for his thoughtful comments in response to our article, "Whole-Body CT Screening: Spectrum of Findings and Recommendations in 1192 Patients" (1). We agree with Dr Hall that guidelines for whole-body CT screening are necessary. In our opinion, these guidelines should include (a) delineation of an appropriate CT screening population (eg, screening inclusion and exclusion criteria), (b) implementation of a report lexicon for standardized communication of results, and (c) development of callback and outcome monitoring systems. As Dr Hall states, the lessons learned from mammography may be beneficial for whole-body CT screening and other screening tests. In fact, we recently completed a new study, the results of which are now being prepared for publication, in which we developed a modified Breast Imaging Reporting and Data System for classifying CT screening findings and recommendations.
Another crucial issue raised by Dr Hall is the myriad of incidental findings detected at diagnostic, as well as screening, CT. This issue threatens to become even more important in the future because the capability to detect small lesions at CT is increasing faster than the capability to characterize them. As the demand for CT continues to rise, the number of persons with incidentally discovered findings is likely to rise, as well. Guidelines similar to those developed by the Fleischner Society for small pulmonary nodules (2) would be helpful for the rest of the body. Unfortunately, guidelines for abdominal CT may be more difficult to develop than those for chest CT. A unique challenge in the abdomen is that nonenhanced CT is rarely adequate for lesion characterization; many incidentally discovered lesions will require intravenous contrast material–enhanced CT, or another imaging modality, for more complete assessment. In addition, separate sets of guidelines may be required for each abdominal and pelvic organ.
In our article, we reported a high number of findings and recommendations with whole-body CT screening. We strongly agree with Dr Hall that standards and guidelines are necessary for this and other screening imaging examinations.
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This article has been cited by other articles:
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  I. M. Burger, N. E. Kass, J. H. Sunshine, and S. S. Siegelman The Use of CT for Screening: A National Survey of Radiologists' Activities and Attitudes Radiology, July 1, 2008; 248(1): 160 - 168. [Abstract] [Full Text] [PDF]
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R. Dyer, D. J. DiSantis, and B. L. McClennan Simplified Imaging Approach for Evaluation of the Solid Renal Mass in Adults Radiology, May 1, 2008; 247(2): 331 - 343. [Abstract] [Full Text] [PDF]
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