A new study from Johns Hopkins School of Medicine in Baltimore is questioning the value of computed tomography scans for lung cancer screening. Published in the Jan. 15 issue of the Journal of the American Medical Association, the report argues that the cost of such scanning and the harm of unnecessary, invasive procedures resulting from that testing may outweigh the benefits.Working with published lung cancer studies and a national cancer database, Dr. Parthiv J. Mahadevia and colleagues developed a computer-simulated model to compare annual helical computed tomography screening with no screening for 100,000 hypothetical 60-year-old subjects who were current, quitting or former heavy smokers. According to Mahadevia, now a research scientist at Medtap International in Bethesda, Md., results indicate that diagnostic scanning would prevent 553 of an estimated 4168 lung cancer deaths for heavy smokers over a 20-year period, or a 13 percent drop in mortality. However, with screening, the test group could also expect 1186 unnecessary, invasive procedures based on false-positive readings.Based on the simulation, the scientists found the diagnostic screening to be most cost-effective for people between 55 and 65 years of age, with gains in cost-effectiveness not appearing until the third year of follow-up because of costs associated with false-positive diagnosis in earlier years. Benefits seem to drop dramatically for those quitting smoking and for former smokers.With this study, the researchers do not completely rule out the use of computed tomography screening for lung cancer. Instead, they make a strong case against mass screening for the disease because there is no evidence of the early-diagnostic efficacy of this type of medical imaging.