SECTION 3 Preventive medicine and public health Box 16-2 Lung Cancer Screening: Simulation Models, Stage Differences, and RCTs possibilities.Conducting a randomized controlled trial(RCT) of a CT were then published, with conflicting resu/s, ie ng with helical The development of new diagnostic methods offers new screening curable cancers. Several modeling studies of screen w screening intervention is arduous and time-consuming. In the absence of RCTs, preventive medicine practitioners sometimes rely In 2002 the National Lung Screening Trial was launched. More than studies or mathematical modeling of screening inter 53,000 participants were randomized to either three annual helical through cost-utility analysis(see Chapter 6). The history of CI scans or chest x-ray films. In 2011 the results were published cer screening illustrates the pitfalls of such sources of There were 247 deaths from lung cancer per 100,000 person-years in the low-dose CT group and 309 deaths per 100,000 person-years in Lung cancer remains the number-one cause of cancer mortality in from lung cancer with low-dose CT screening of 20.0%. Although the United States. For a long time, there was no viable way to screen less than expected by proponents, this mortality reduction was still for lung cancer, Chest x-ray and sputum examination had been clinically significant. However, the trial also likely showed evidence tested but only led to more invasive testing, with no difference in of overdiagnosis; even after the gap in detection time between the ortality. Then, helical computed tomography (CT) imaging two screening modalities closed, the screened group had more cancer became available and seemed to offer the capacity to find small lung than the control arm. cancer nodules early. Several uncontrolled trials were perfor and showed higher cancer detection rate. Several authorities advo This example shows that modeling can inform decisions when no cated to start screening immediately based on the difference in the evidence is available. However, given the significant biases at work distribution of cancer stages found in the screened group from that to have uncontrolled studies overestimate screening benefits, there is usually found in clinical practice; patients in the screened group were no alternative to rigorous rCts luch more likely to be diagnosed with early and small, potentially Counseling to promote good health habits and prevent ndividuals for the specific set of conditions and diseases disease(health promotion) most likely to be found in persons of a certain age and n Immunizations and chemoprophylaxis to prevent spe- gender, and its use has been advocated by experts on preven cific diseases(primary prevention tive medicine in Canada and the United States. Many prac- titioners who emphasize preventive medicine prefer to see The first report of the USPSTF was issued in 1989. Since their patients for checkups more often than may be recom then, there have been regular literature reviews and updated mended, such as I or 2 years, to maintain a relationship of creening recommendations for the entire spectrum of di trust and to repeat health promotion messages that are eases amenable to screening, counseling, and prophylaxis. important for efforts to change behavior Recommendations are upgraded regularly and are available References ⅣV. SUMMARY I. Berwick DM: Screening in health fairs: a critical review of benefits, risks, and costs. JAMA 254: 1492-1498, 1985 2. Nelson HD et al: Screening for ovarian cancer: a brief update The goal of secondary prevention is the detection of disease http://www.uspreventiveservicestaskforce,org/3rduspstf/ or risk factors in the presymptomatic stage, when medical ariancan/ovcanup. htm. environmental, nutritional, and lifestyle interventions can be 3. Nelson HD, Tyne K, Naik A, et al: Screening for breast cancer: most effective. Screening is done in a community setting, an update for the U.S. Preventive Services Task Force. Ann whereas case finding is done in a clinical setting. To be ben stern Med151:727-737,2009 eficial and cost-effective, community screening programs 4. Elmore JG, Armstrong K, Lehman CD, et al: Screen must fulfill various requirements on the health problem to breast cancer. JAMA 293: 1245-1256, 2005 be detected, the screening test used, and the system available JD 77-84,1976 to provide health care for people with positive screening 6. Christopherson WM, Parker JE, Drye )C: Control of cervical results. Selection, lead-time, and length biases can lead to cancer:preliminary report on a community program. JAMA overestimates of benefit from screening, particularly the 182:179-1 program detecting cancer. Although multiphasic screening 7. Elmore JG, Barton MB, Moceri VM, et al: Ten-year risk of false seeks to make the process efficient by searching for ma positive screening mammograms and clinical breast exami conditions at the same time, the high incidence of fals tions. N Engl J Med 338: 1089-1096, 1998. positive results and associated problems have made this tech 8. Bates B, Yellin JA: The yield of multiphasic screening. JAMA nique less successful than was originally anticipated. Genetic 222:74-78,1972 screening introduces a new subset of requirements for 9. olsen dm, Kane rl proctor ph: a controlled trial of multi screening tests, including clinical validity and clinical utilit hasic screening. N Engl J Med 294: 925-930, 1970 10. Yarnall Ks, Pollak Kl, Ostbye T, et al: Primary care: is there Historically, the periodic health examination has been the most common method of case finding. Because of disap enough time for prevention? Am J Public Health 93: 635-641 pointing benefits, however, it is now being replaced by life- 11. Robin NH, Tabereaux PB, Benza R, et al: Genetic testing in timehealth monitoring This approach focuses on monitoring cardiovascular disease. J Am Coll Cardio! 50: 727-737, 2007