Study Questions Early CT Screening for Lung Cancer
March 7, 2007
A major new study by researchers at New York's Memorial Sloan-Kettering Cancer Center indicates that routine screening with low-dose CT scans of people at high risk for lung cancer does not in fact reduce the risk of death and may actually lead to unnecessary surgeries and negative health impacts. The study appeared in the March 7 edition of the Journal of the American Medical Association (JAMA).
These findings are in stark contrast with a study conducted by researchers at New York-Presbyterian/Weill Cornell Medical Center in Manhattan just over six months ago which suggested that low-dose CT screening resulted in a 10-year survival rate of better than 90 percent for patients whose tumors were removed shortly after they were found.
"The formulation of screening policy should await the rigorous assessment that will be provided by ongoing randomized controlled trials," said William Black, MD, Chest Imaging Division Director at Dartmouth-Hitchcock Medical Center and a professor of Radiology and Community and Family Medicine at Dartmouth Medical School. Black, along with John Baron, MD, who is also a professor of Community and Family Medicine at Dartmouth Medical School, co-authored an editorial that also appears in the March 7 edition of JAMA, which says that there are a number of possible explanations for the wide discrepancies between the two studies, and which advocates for waiting to see the results of two major ongoing randomized clinical trials, the National Lung Screening Trial in the United States and the NELSON Trial in Europe.
"Randomized controlled trials are the most reliable method for obtaining accurate assessments of the benefits and harms of screening in the underlying population," say Black and Baron. "With this design, differences in outcome can be attributed to the intervention without reliance on highly modeled analyses with problematic assumptions. Although expensive and time-consuming, rigorous trials of cancer screening are far more cost-effective than what might be the alternative-widespread adoption of costly screening interventions that cause more harm than good."
In their editorial, Black and Baron cite a number of possible explanations for the variances in the results of the two studies including chance, a difference in the populations or screening interventions, the accuracy of the lung cancer prediction model that was used by the Memorial Sloan-Kettering researchers and the way in which the researchers ascertained the deaths of patients from lung cancer. However Black and Baron say that the best explanation for the contrasting results is likely a difference in the primary outcome measures - mortality in the most recent study versus survival in the earlier I-ELCAP study.
The authors say that while these two measured are often perceived as complementary, prolonged survival does not necessarily imply reduced mortality in the general population. Black and Baron also say that the more recent study offers more insight into the population effect of CT screening and the potential harms than the earlier study.