Thoracic Imaging 2003 - Society of Thoracic Radiology

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Principles and ethics of lung cancer screening Caroline Chiles, M.D. Objectives The participant will understand the biases of cancer screening (length-time bias, lead time bias, and overdiagnosis), and the necessary elements of informed consent for cancer screening programs. Introduction Screening is the application of a test to detect a disease or condition in an individual who has no known signs or symptoms of that disease or condition. The goal of imaging studies for cancer screening is the early detection of disease at a point when treatment is more effective. The assumption is that early detection (the preclinical phase of disease, prior to the onset of clinical manifestations of the disease) will lead to a more favorable outcome. In lung cancer, the improved survival in Stage I disease as a result of surgical resection fuels the effort towards finding an effective screening test. Lung cancer meets many of the criteria required for screening programs to be effective. It is a disease that affects a large number of people, and which has serious consequences (150,000 lung cancer deaths in the US in 2002). It is possible to choose a population at increased risk (smokers, former smokers) in whom a preclinical phase of the disease is detectable (the asymptomatic patient with a solitary pulmonary nodule). Screening tests can detect lung cancer not only prior to its clinical presentation, but prior to a critical point – metastatic disease. Both CXRs and CTs are widely available, “affordable” examinations with little morbidity. Most importantly, an individual with an early stage lung cancer may have surgically respectable disease, and the potential for cure. Principles of cancer screening The preclinical phase of lung cancer can be divided into two parts: (1) the interval from the onset of disease, before the disease is detectable to the time at which the disease becomes detectable by the screening test, and the interval from the time at which the disease is detectable by the screening test to the onset of signs and symptoms. This is most clearly shown by use of time lines, which are adapted from Black and Welch, AJR 1997; 168: 3-11. The lead time is defined as the interval between the diagnosis of a disease at screening and the time it would have otherwise been detected due to the appearance of clinical signs and symptoms. The amount of lead time that can be gained by a screening test is a function of the time from disease detectability to the onset of symptoms and the frequency of testing. Figure1 The lead time bias describes the comparison between the survival time in patients who are not screened and those who are. Even if intervention in the course of disease has no effect, the individual who has screening-detected cancer can appear to have a longer survival than the individual who has a diagnosis made on the basis of clinical presentation, as survival is measured from the date of diagnosis, rather than from the true onset of disease. The rate of progression of screening-detected lung cancers cannot be known at this time and therefore it is impossible to accurately adjust survival times to account for lead time. Figure2 Length bias describes the tendency of screening to detect slowly growing cancers, rather than rapidly progressing ones. As can be seen by looking at the timeline in Figure 1, if the detectable phase of disease is long, there is a greater likelihood that a screening test will be performed and the disease will be detected. More rapidly growing tumors have a shorter detectable preclinical phase and are less likely to be detected by a screening examination prior to the onset of symptoms. Therefore, lung cancer screening programs are more likely to detect slowly growing lung cancers. Overdiagnosis bias has been become a widely appreciated phenomenon as a result of prostate cancer screening using PSA. Overdiagnosis relates to the number of cases that would not have caused the death of the patient even without screening. The survival in these patients may be erroneously attributed to early detection and treatment. The biases inherent in screening can be reduced with a randomized controlled trial in which effectiveness is measured by disease-specific mortality --- comparing the number of deaths from lung cancer in a screened population to the number of deaths from lung cancer in an unscreened population. Ethics of lung cancer screening The ethics of lung cancer screening can be considered from two perspectives: screening as part of a research study evaluating lung cancer screening and screening within a clinical environment. Research involving human subjects is governed by the Declaration of Helsinki, first adopted by the World Medical Association in 1964, and most recently revised in 2002. (http://www.wma.net/e/policy/17-c_e.html) The Declaration contains 32 ethical principles for medical research. A basic 207 WEDNESDAY
WEDNESDAY 208 principle is that “conditions related to the well-being of the human subject should take precedence over the interests of science and society”. The Declaration of Helsinki also states that “The benefits, risks, burdens and effectiveness of a new method should be tested against those of the best current prophylactic, diagnostic, and therapeutic methods. This does not exclude the use of placebo, or no treatment, in studies where no proven prophylactic, diagnostic or therapeutic method exists.” This introduces the concept of equipoise. The principle of clinical equipoise was re-defined by Dr. Barry Freedman as “a genuine uncertainty within the expert medical community regarding the comparative therapeutic methods of each arm in a trial.” At the start of a trial, there must be a state of clinical equipoise regarding the merits of the two arms. The trial must be designed in such a way as to expect that clinical equipoise will be disturbed. In this case, the expert medical community must agree that the relative value of screening for lung cancer with one technique (CT) versus another (CXR) is uncertain. Herein lies some of the controversy over lung cancer screening. Screening for lung cancer with either CXR or CT has not been proven to change the outcome – to reduce the likelihood of death from lung cancer – and this must be explained clearly to participants in either a research study or within a clinical environment. In addition, individuals in both research screening programs and clinical screening programs must be informed of the risks and benefits of lung cancer screening. The risks of false positive examinations, particularly with respect to the risks inherent in the work-up of both incidental and false-positive findings must be thoroughly explained. The risk that a screening examination is incorrectly interpreted – and is a false negative should be included. Even a true negative examination must be described as a risk, in that it may prejudice the patient from recognizing and acting on symptoms of disease that develop at a later date. The informed consent should also include information about the risks of radiation exposure, and about intravenous administration of contrast material, if applicable. In programs that are screening patients who are self-referred, the radiologist assumes the role of personal physician. In this regard, the radiologist must not only communicate the results of the examination to the patient, but must be available to assist the patient in the evaluation of any abnormality revealed by the screening examination. An unresolved issue remains, and will only add to this controversy over time. The ethical dilemma for society is – who should bear the financial burden of the evaluation of findings on screening examinations? REFERENCES Black WC, Welch HG. Screening for disease. AJR 1997; 168: 3-11 Freedman B. Equipoise and the ethics of clinical research. New Engl J Med 1987; 317:141-145 Herman CR, Gill HK, Eng J, Fajardo LL. Screening for preclinical disease: Test and disease characteristics. AJR 2002; 179:825- 831 Kramer BS, Brawley OW. Cancer screening. Hematolog/Oncol Clin N Amer 2000; 14(4): 831-848 Obuchowski NA, Graham RJ, Baker ME, Powell KA. Ten criteria for effective screening: Their application to multislice CT screening for pulmonary and colorectal cancers. AJR 2001; 176: 1357-1362 Soda H, Oka M, Tomita H, Nagashima S, Soda M, Kohno S. Length and lead time biases in radiologic screening for lung cancer. Respiration 1999; 66:511-517
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The Society of Thoracic Radiology T
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Dear Friends, Welcome to Miami Beac
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Continuing Medical Education Credit
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Warren B. Gefter, MD University of
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Ernest M. Scalzetti, MD SUNY Upstat
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Registration Hours Saturday, March
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Program Committee Ella A. Kazerooni
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Small Airway Disease Americana 3 Mo
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Benjamin Felson Memorial Lecture Am
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Session 2-B Concurrent Session Clin
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Workshops (choose 1) 1:00 - 1:45 D1
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Sunday
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March 2, 2003 General Session Sunda
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SUNDAY 46 One type of direct-readou
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CT-PET Imaging Suzanne Aquino, M.D.
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SUNDAY 58 an accompanying decreased
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SUNDAY 60 Radiofrequency Ablation i
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SUNDAY 62 17. Sewell PE, Vance RB.
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SUNDAY 64 cal ventilation will be r
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SUNDAY 66 radiologic, and histopath
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SUNDAY 68 application. The untreate
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SUNDAY 70 The Expanded Spectrum of
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SUNDAY 72 Hypersensitivity Pneumoni
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SUNDAY 74 Small Airway Diseases Mic
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SUNDAY 76 The “Head-cheese Sign
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SUNDAY 78 “Holes” in the Lung:
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SUNDAY 80 Pleural Effusions Gerald
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SUNDAY 82 Asbestos Related Pleural
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SUNDAY 84 Other Pleural Neoplasms S
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SUNDAY 86 Image-Guided Therapy of M
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Notes 88
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March 3, 2003 General Session 7:00
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Cardiac MRI: Established Indication
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Cardiac MRI: New Developments Gauth
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5. The volume of contrast medium re
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Acute Aortic Syndrome Ernest M. Sca
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as well as separation of the cusps
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Pulmonary Veins: Imaging for Radiof
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Imaging of Cardiopulmonary Support
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plied to the hollow fibers by an ex
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swelling of the entire leg, calf sw
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Multi-channel Pulmonary CTA: New Te
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terminate scintigrams, CT correctly
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CT Strucural and Functional Imaging
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curves (TDCs) are generated by manu
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7. Crawford T, Yoon C, Wolfson K, e
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80. Fleischmann D, Rubin GD, Bankie
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127 MONDAY
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129 MONDAY
Page 99 and 100: REFERENCES Bergin CJ, Rios G, King
Page 101 and 102: Notes 134
Page 103 and 104: March 4, 2003 General Session 7:00
Page 105 and 106: Adult Manifestations of Congenital
Page 107 and 108: will usually display the limbs of t
Page 109 and 110: Imaging of the Pericardium Paul L.
Page 111 and 112: Cardiomyopathy Martin J. Lipton, M.
Page 113 and 114: TUESDAY 150 Nuclear Cardiology Upda
Page 115 and 116: TUESDAY 152 ties. The predominant 1
Page 117 and 118: TUESDAY 154 Imaging protocols: Util
Page 119 and 120: Manpower Shortage in Radiology: Sol
Page 121 and 122: 159 TUESDAY
Page 127 and 128: NIBIB Update for Thoracic Radiology
Page 129 and 130: vertically along the right atrium t
Page 131 and 132: Multidetector Pediatric Chest CT: P
Page 133 and 134: The Spectrum of Pulmonary Infection
Page 135 and 136: Immune deficiency occurs frequently
Page 137 and 138: TUESDAY 180 The Internet and the Pr
Page 139 and 140: TUESDAY 182 Workshop A1: Lymphoma:
Page 141 and 142: TUESDAY 184 Digital Images: Camera
Page 143 and 144: TUESDAY 186 Analysis of Mediastinal
Page 145 and 146: Unusual Manifestations of Lung Canc
Page 147 and 148: Wednesday
Page 149: March 5, 2003 General Session Wedne
Page 153 and 154: WEDNESDAY 210 years and a current o
Page 155 and 156: WEDNESDAY 212 lesions generally mim
Page 157 and 158: WEDNESDAY 214 capable of studying t
Page 159 and 160: WEDNESDAY 216 Small T1 Lung Cancer:
Page 161 and 162: WEDNESDAY 218 REFERENCES Seely JM,
Page 163 and 164: WEDNESDAY 220 Therefore, radiologis
Page 165 and 166: WEDNESDAY 222 sectional area varies
Page 167 and 168: WEDNESDAY 224 Lung Cancer Staging A
Page 169 and 170: Metastatic Disease to Lung Gordon L
Page 171 and 172: Thoracic Metastates from Osteosarco
Page 173 and 174: STR tutorial: Use of MD CT reconstr
Page 175 and 176: ogenic edema, fat embolism, heroin
Page 177 and 178: WEDNESDAY 236 Pulmonary Arterial Hy
Page 179 and 180: WEDNESDAY 238 pathological process,
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Page 183 and 184: THURSDAY 250 Pulmonary Tuberculosis
Page 185 and 186: THURSDAY 252 1. Clinical criteria:
Page 187 and 188: THURSDAY 254 AIDS patients are also
Page 189 and 190: THURSDAY 256 Viral Infection on HRC
Page 191 and 192: THURSDAY 258 Imaging of Coccidioido
Page 193 and 194: THURSDAY 260 from the laryngeal sur
Page 195 and 196: THURSDAY 262 Inflammatory Diseases
Page 197 and 198: Virtual Endoscopy in the Thorax: Pr
Page 199 and 200: Notes 269 THURSDAY
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SECOND LEVEL THIRD LEVEL
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