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Editorials |
1 From the Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905. Received May 28, 2002; accepted June 7. Address correspondence to F.E. (e-mail: earnest@mayo.edu).
Index terms: Cancer screening • Editorials • Informed consent
The radiology community has become divided over how computed tomographic (CT) technology should be applied to screening patients for cancer. Some advocate unrestrained availability of screening with CT to patients with sufficient interest and economic resources, arguing for patient autonomy in personal health matters. This view is primarily espoused by entrepreneurs in freestanding centers who have adopted a market-based approach to the provision of medical services. Others look at the lack of data to support the benefit from such screening programs and either do not offer screening or try to limit screening studies to specific clinical trials or specific requests from physicians in their practices. The financial ramifications of screening are huge, and conflict of interest and self-referral are substantial ethical issues in this debate. The American College of Radiology and the Food and Drug Administration have policies that discourage whole-body screening (1,2) but are silent about organ-specific screening. The Society of Thoracic Radiology has published a statement in which it discourages the use of low-dose CT for lung cancer screening at this time (3).
Through long and arduous debates about the benefits, risks, and costs of screening with mammography, we are all becoming more educated about the sources of bias in screening studies, the very large numbers of subjects needed to provide statistical power for any screening trial, and the lengthy follow-up needed to demonstrate a mortality benefit (4). There is the problem of recruiting a representative sample of individuals. We know that selection bias confounds the results of all single-arm observational studies. There is overdiagnosis, that is, the identification of prevalent lesions that may or may not lead to morbidity or mortality. There are lead-time and length-time biases that invariably improve apparent survival in the screened population whether or not a true mortality benefit can be identified. There are randomization problems associated with the perceived benefit or harm of the proposed test. If the benefit is perceived as great, there is crossover from a control group to a screening group. Conversely, if there is a perceived harm in the screening process, there is attrition of subjects initially recruited to the study. For these and other reasons, few, if any, screening trials have satisfied all the requirements of an ideal randomized controlled trial.
Our department, like other academic departments, has taken the stance that too little is known about CT screening to recommend it to our patients. However, we are increasingly faced with many "Trojan horse" referrals for vague complaints that we now recognize as surrogate indications for screening examinations. In other words, we cannot restrain the interest in CT screening or the demand for these examinations. Patients have access to lots of information of varying quality and overwhelming quantity. They also are inundated with advertising that suggests screening is life saving, supported by testimonials from popular celebrities and entertainers. This is the reality of our current environment, and patients with motivation and resources to seek screening will not wait for the results of randomized controlled trials.
Lung cancer is the perfect paradigm for looking at the complex issues surrounding CT screening in the absence of randomized controlled trials. It is the most common cancer and the most common cause of cancer deaths in both men and women. Spurred on by improved survival among some lung cancer patients, researchers have tried to find the best examination to identify lung cancer at an early stage. The Mayo Lung Project was one such study. It was undertaken in the early 1970s to assess the benefit of screening by using regular chest radiography and sputum cytologic analysis for the detection of early lung cancer. Now, more than 20 years later, findings of this study and of others demonstrated that regular screening of smokers with chest radiography fails to reduce mortality (5). Although an increased number of lower-stage cancers were identified in the screened group, and survival appeared to be increased, there has been no benefit of mortality reduction demonstrated from screening by using chest radiography.
In truth, little is known about the benefits, risks, and costs of screening by using CT. We do know that CT is much more sensitive than is chest radiography in the detection of lung nodules. It would make sense that CT would have much greater benefit than would chest radiography as a screening tool. There are now data from some observational studies that demonstrate both the sensitivity of CT and the lack of specificity for the identification of lung cancer (6,7). Henschke et al (6) and Swensen et al (7) demonstrated that there are a plethora of lung nodules in otherwise healthy individuals. The percentage of incidental or benign nodules ranges from 27% to more than 70%, and both unrecognized nodules and new nodules are identified at follow-up CT examinations. Our ability to identify so many nodules is undoubtedly related to many factors. Important factors in nodule detection are the section width of image reconstruction and dynamic viewing of imaging data. Other factors include the prevalence of endemic granulomatous diseases. Even in a population with a higher risk, such as that of smokers, only 1%–2% of uncalcified lung nodules are cancers (7).
Findings in a report of mass CT screening by Sone et al (8) demonstrate some of the difficulties that are encountered when both smokers and nonsmokers are screened. We are recognizing that many incidental neoplasms, identified in elderly patients, have uncertain significance with regard to morbidity and mortality (9). There is a growing consensus that randomized controlled trials are necessary to demonstrate a reduction in lung cancer mortality by using screening chest CT. Several trials are in the final stages of planning, and the National Lung Cancer Screening Trial is now underway in the United States. Results of such studies may have a greater impact on health policy decisions in the long term than on our need for a response to patients today.
We now believe it is necessary to reconsider our departmental policy for screening and would suggest a similar reconsideration by the American College of Radiology and other medical organizations. The radiology community could better serve patients by elevating the dialogue and decision making regarding CT screening that occurs every day in the midst of conflicting arguments and advice. We should advocate a position that addresses the reality of our current screening conundrum and moves us away from the polarities of unrestrained free market advocacy or an unwavering demand for data that will be available in only a decade or more. This position, this middle ground or third path, is informed consent.
Informed consent will provide patients with correct information about the benefits, risks, and alternatives for screening as we currently understand them and will positively influence the practice of all who would choose to offer CT screening examinations.
What do we mean by informed consent? The content of the consent would be written, tailored to each specific type of screening examination, and would provide information sufficient to meet the reasonable person standard of informed consent adopted as law in many states. We will use chest CT for lung cancer screening as an example. On the basis of our experience (7), the essential information provided to patients might include the following points:
1. There is a chance that a small lung cancer may be detected and that surgical removal of a small cancer could be life saving.
2. CT is more sensitive in the detection of lung nodules than is chest radiography, and there may be a benefit to screening with CT that was not apparent in previous screening studies with chest radiography.
3. There is no established benefit of mortality reduction from lung cancer screening with any method.
4. More than one-half of previous smokers will have at least one nodule detected with chest CT used as a screening tool, and most of these will require at least three additional CT examinations for complete evaluation. Further investigation of these nodules could include biopsy and resection, which have an additional risk of morbidity and mortality.
5. Overall, more than 98% of these nodules are benign, or not cancer. Only 1.5% of nodules are found to be cancers among smokers who undergo screening with chest CT.
6. An additional 10% of patients will have new nodules identified at follow-up CT examinations.
7. An additional 10% of patients will have some other abnormality outside of the lung that will require follow-up imaging. Most of these abnormalities are of no consequence to health.
8. Each CT examination of the chest performed with a low-dose technique delivers a radiation dose to the lungs that is equivalent to that of 10 two-view chest radiographs and a dose to the breasts that is equivalent to that of one mammographic film of each breast. A CT examination of the chest performed by using a routine diagnostic technique delivers a radiation dose approximately 10 times higher than that of the low-dose technique. (These dose values are protocol specific and vary among institutions.) A very small number of patients may develop a cancer related to radiation exposure, and that number is probably too small to be demonstrated in any clinical trial.
If such a consent process were adopted, it would necessarily be organ specific, and an additional consent for other CT screening studies would be necessary to provide appropriate informed consent.
We believe that this kind of information, provided in writing, would give patients the information that a reasonable person would want to know prior to having a screening chest CT examination. National radiology societies, such as the American College of Radiology, the Radiological Society of North America, or the American Roentgen Ray Society, would be best equipped to provide this information and to regularly monitor and evaluate ongoing research. By adopting the informed consent approach, the radiology community could be a catalyst for providing important information to patients, families, and communities and could thereby help them to make better, more informed choices.
REFERENCES
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