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Counterpoint |
1 Department of Radiology, UMDNJ–New Jersey Medical School, 150 Bergen St., UH C318, Newark, NJ 07103.
Received April 1, 2003; accepted after revision August 21, 2003. Dr. Levatter offers a number of criticisms with respect to the issues I raised concerning fullbody screening CT [1, 2]. Unfortunately, his comments are informed by the same pervasive disingenuousness that characterizes the advertising by screening advocates.
Levatter relates that little notice is given to the modern economic concept of the subjectivity of value. In support of that notion, he offers four examples, ecumenically including the restraints exercised by certain devout Christians and Jews. The fallacy behind these examples is that observant adherents will not sin despite the temptation. They know full well the implications of violating their religious principles. CT screening is substantively different. The potential customer does not have the same perfect information on which to make a judgment about the merits of an alluring offer of service at a price. The imbalance between purveyor knowledge and patient ignorance allows screening centers to manipulate the message to induce business. This might be fine in the general marketplace, where the consequences of the purchase of a product are not injurious. However, the remote chance of finding a treatable disease and the more likely outcome of a false-positive finding place the unwitting and hitherto healthy individual in jeopardy of further examinations and interventions.
Levatter acknowledges that ethical business conduct and the legal concept of informed consent mandate that issues of prevalence be conveyed to potential customers. Yet he cannot deny that, for the most part, the public has not been adequately apprised of the uncertainties and limitations of full-body CT. The message relayed loudly and clearly through the media is that your life depends on undergoing this study.
The aim is to scare you with the prospect, rare as it may be, that something bad but curable will be found. Such advertisements do not relate that seldom will a correctable, life-threatening abnormality be found in healthy people by this technique. Inasmuch as false-positive results are inevitable and more common than true-positive results in asymptomatic individuals, CT screening will compel the ordering of unnecessary further studies, engendering added cost and anguish. Value is subjective, but for medical procedures it should be derived from data as well as from propaganda and puffery. So Levatter's notion of the primacy of the perception of consumer value over the responsibility of the informing physician for the representation of fact should not apply here.
Also to be questioned is Levatter's proposition that a spectrum of technical possibilities is inherent in full-body screening CT. Levatter makes the point with reference to the barium enema examination. Certainly, quality will vary widely when an imaging technique is operator-dependent. But CT does not fall under this rubric because the resemblances among various helical CT protocols are much greater than the differences. The only real quantum improvement for the detection of disease can come from the introduction of IV contrast material as an integral component of the screening examination.
Levatter's argument is chimeric when he proffers that the routine administration of contrast material is an option to screening centers to improve accuracy. Screening centers that are not located in hospitals will never make contrast administration standard, and everyone knows that. Using contrast material would mean additional costs and charges for the injectable agent, the need for informed consent that could dissuade a potential customer, prescreening for allergy and kidney disease, assumption of the risk of reaction to the contrast material, a greater susceptibility to lawsuits, the necessity of a physician or nurse on-site, and higher insurance premiums—to name just some of the financial and administrative burdens. Consequently, only screening centers at hospitals could afford to take on the obligation of contrast administration with screening CT.
Levatter compares the appropriateness of full-body screening CT with the well-established use of mammography for the assessment of breast cancer, which is itself a controversial topic. The purpose of mammography is to detect a lesion amenable to biopsy, not to immediately render a diagnosis of malignancy. A mammogram with positive findings is followed up by procedures to obtain tissue, which are usually performed in an outpatient setting. The publicity that seeks to promote screening CT really relates to the ability of the technique to reveal cancer arising in the renal parenchyma. However, for kidney malignancy, histologic confirmation of CT findings requires more than an outpatient procedure. Moreover, mammography is performed regularly according to a well-defined schedule for the initial and subsequent studies. No one has defined an appropriate time between successive screening CT examinations, despite the fact that all other well-recognized surveillance tests in adults have been validated by the determination of an appropriate interval.
With respect to his comments on renal cell carcinoma, it is clear that Dr. Levatter has inappropriately conflated two distinct concepts. Renal cancer affects one in 650 individuals (combining both sexes) some time in the fifth or sixth decade of life. But a single screening CT examination does not occur continuously over a score of years but only at one point in time. Thus, especially in patients in their 40s, unenhanced screening CT at any particular examination will reveal a hypernephroma in only one in 22,000 men, not one in several hundred. Furthermore, Brant-Zawadzki [3], a vigorous proponent of CT screening, in a study of 1,777 patients found 20 putative renal lesions exclusive of stones and benign cysts. Among this group of 20 were two carcinomas and one angiomyolipoma. What were the other 17? If they were truly lesions, they could not be normal variants. One has to conclude that with respect to cancer (and I include the one angiomyolipoma here), 17 (85%) of these 20 putative lesions were actually false-positive results. Such determinations were probably made after surgery on hospitalized patients. Should this evidence not be made available to potential consumers who are considering the value of screening CT?
Pharmaceutical advertisements come under the purview of the Food and Drug Administration. But messages promoting imaging that involves direct payment by the consumer are essentially unregulated. Levatter argues for the free exchange of information, which is a hallowed tenet of a market economy in a capitalist society. But the Hippocratic injunction to do no harm is an even more important touchstone in the interchange between physicians and patients. Brant-Zawadzki's data indicate that many more people with "positive" findings on CT screening of the kidney were likely made worse off than were improved.
Levatter also calculates that the accumulation of possibilities for the detection of malignancies outside the kidney is another compelling reason for the worried well to undergo full-body screening CT. But let us remember the rules. The technique has clinical value if it reveals more true-positive than false-positive findings of a disease for which early detection eventually results in a cure. Consequently, Levatter's choice of pancreatic cancer is an inapt example. Aside from a very few case reports over the 27-year history of whole-body CT, malignancy in the pancreas is never detected in time, leaving only false-positive findings associated with prolonged survival. The only thing gained would be results of studies suggestive of disease when no disease was actually present. Moreover, cure rates for lymphoma are not addressed by screening CT because the likelihood is very low in the asymptomatic individual that a slightly enlarged lymph node revealed by screening CT is, in fact, lymphomatous. Here, too, false-positive findings are overwhelming. Levatter asserts that these facts are noncontextual, an assertion that is nonsensical. Apparently, the real lack of efficacy of screening CT is not relevant for him.
Moreover, Levatter also considers that the analyses provided by me were "methodologically uncharitable." This is a peculiar charge by one interested in economic principles. Methods are not judged by the mercy they exude, but by the vigor they impose. He professes that screening CT has received a favorable reception. But judging from the recent marked decrease in advertisements for it in both the print and the electronic media, the bankruptcy of previously high-flying screening companies, and the imposition of regulations in several states constraining patient-initiated CT examinations, it is now apparent that the public has largely turned away from screening CT. For the most part, the technique has received and continues to receive a bad press, especially in the medical literature. Unless specific data can be provided to support the efficacy of fullbody screening CT, it is probably getting just what it deserves.
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  C. D. Furtado, D. A. Aguirre, C. B. Sirlin, D. Dang, S. K. Stamato, P. Lee, F. Sani, M. A. Brown, D. L. Levin, and G. Casola Whole-Body CT Screening: Spectrum of Findings and Recommendations in 1192 Patients Radiology, November 1, 2005; 237(2): 385 - 394. [Abstract] [Full Text] [PDF]
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