A large international study looking at the use of controversial, and expensive, computed tomography (CT) scans to screen for lung cancer has determined that the technology does not reduce deaths from the disease. The finding directly conflicts with a widely publicized study from last October that estimated 80% of lung-cancer deaths could be prevented by CT screening, and has galvanized the two sides of the debate (see BusinessWeek.com, 10/25/06, "Lung Cancer: Hope for Early Detection").
The issue is one of the most critical in the cancer world. Lung cancer is by far the largest cancer killer, and is rarely detected before it is too late to treat. Last year the American Cancer Society estimated that approximately 175,000 people in the U.S. were diagnosed with the disease and 162,000 died from it. That's a higher level of fatalities than from colon, breast, and prostate cancer combined.
The controversy turns on whether early detection of lung cancer can actually save lives. The new study, conducted by researchers from Memorial Sloan-Kettering Cancer Center in New York and published in the Mar. 7 issue of the Journal of the American Medical Association, reported that CT scans found nearly three times as many lung cancers as would have been predicted in the 3,246 current and former smokers screened. However this early detection and treatment did not lead to a corresponding decrease in advanced lung cancers or a reduction in deaths. "Early detection and additional treatment did not save lives, but did subject patients to invasive and possibly unnecessary treatments," said Dr. Peter Bach of Sloan-Kettering, the lead author of the study.
Rival Researcher Objects
The findings were immediately disputed by Dr. Claudia Henschke of Weill Cornell Medical Center in New York, author of the October study. She took issue with the methodology and calculations of the Sloan-Kettering group. "They focused on too short a period of time, and their model underpredicted deaths," she says. "If you carefully look at their data, it actually confirms our results." However, Henschke's own study, in the Oct. 26 issue of the New England Journal of Medicine, was criticized for having no unscreened control group for comparison.
The JAMA study was based on data from three ongoing CT-scan screening projects at the Mayo Clinic in Minnesota, the H. Lee Moffitt Cancer Center in Florida, and the Instituto Tumori in Italy. Those data were analyzed by a computer model designed to predict what would happen to a similar population if it wasn't screened. The study found that there were 10 times as many surgeries performed for lung cancer than had been predicted. Nevertheless, there were still 38 deaths due to lung cancer in the group, compared to a predicted 39. The authors said those results are much the same as would have been produced if the subjects had been screened with chest X-rays, an older, cheaper, and more common screening technology.
Lung-cancer experts on the sidelines said both the JAMA and Weill Cornell studies had some validity. Dr. David Johnson, deputy director of Vanderbilt-Ingram Cancer Center in Memphis, admits that "these are the types of things that drive most of us nuts in terms of what the public is reading." He noted that Henschke found that the CT scans were most likely to extend survival if they detected lung cancer at its earlier stages, while the Sloan-Kettering researchers looked at its impact on the cancer at all stages, even the most advanced.
Comprehensive Study Due
All of this could be settled by a large National Cancer Institute study that directly compares CT screening to no screening. But those results are not expected until 2008, and in the meantime people at risk of lung cancer—primarily smokers and former smokers—must make a decision on whether to undergo the test.
It is a costly decision, because CT scans can cost anywhere from $300 to $1,000, vs. $50 for a chest X-ray, and are usually repeated annually for high-risk patients. The test, introduced in the 1970s, spirals low-dose X-rays around the body as it is transported through a metal tube. It is not routinely covered by insurance.
Henschke recommends that, rather than wait for the results of the NCI study, patients who are 50 and older with a history of smoking discuss CT screening with their doctor. The Sloan-Kettering researchers, however, caution that the test itself is not without risk, because it can register false-positive results that can lead to invasive and unnecessary lung biopsies.