A new US study released Wednesday found that people who received chest X-rays to screen for lung cancer showed no better survival rate after four years than those who were not screened at all.
The study published in the November 2 issue of the Journal of the American Medical Association (JAMA), follows a separate study last year that showed X-rays fell short compared to modern CT scans in saving lives from lung cancer, the leading cancer killer worldwide.
This study followed 154,901 participants, about half of whom were women. About 10 percent were current smokers, and the rest were nearly evenly divided between former smokers and people who never smoked. Subjects were either offered a chest X-ray or no screening at all. After four years of follow up, more cancers were found in the chest X-ray group, but there was no significant difference in deaths across either group. Over the course of the 13-year study, “there were 1,696 lung cancers detected in the intervention group and 1,620 lung cancers in the usual care group,” the study said. However, “1,213 lung cancer deaths were observed in the intervention group versus 1,230 in the usual care group.” The findings suggest that even though more cancers are found by chest X-rays, they are not detected early enough to have an impact on survival.
The Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial was led by doctor Martin Oken of the University of Minnesota and presented Wednesday at the annual meeting of the American College of Chest Physicians (CHEST 2011) in Honlulu.
Harold Sox, of Dartmouth Medical School in West Lebanon, New Hampshire, said the findings should end any debate over the effectiveness of lung cancer screening by X-ray. “The PLCO lung cancer study result provides convincing evidence that lung cancer screening with chest radiography is not effective… The study is important for putting this question to rest and providing strong empirical grounds for comparing low-dose computed tomography to a real-world alternative: usual care,” Sox wrote in an editorial that accompanies the JAMA article.
Another major study released last year, the National Lung Screening Trial (NLST), found that current and former heavy smokers saw a 20 percent reduction in lung cancer deaths when screened by low-dose computer tomography (CT scan) rather than X-rays. Helical CT uses X-rays to obtain a multiple-image scan of the entire chest in seven to 15 seconds, compared to the single view given by a chest X-ray.
CT scans provide a more detailed picture of the lungs than chest X-rays so they are better able to identify small tumors, said study author Christine Berg, chief of the Early Detection Research Group at the National Cancer Institute's Division of Cancer Prevention in Rockville, Maryland. “The problem was it [X ray] wasn't finding lung cancer at a small enough size,” she said. “Lung cancer is a very aggressive disease so you have to find it very small in order to cut it out and cure it.”
In the future, X-rays may play a role in lung cancer screening if the technology improves enough to detect smaller tumors. CT scans can be problematic because they can identify many suspicious nodules that aren't positive, Berg added. They're also more costly. Medicare, the U.S. health program for the elderly and disabled, pays about $350 to $370 for a CT scan Institutions generally $750 to $1,000 for the scan while most insurers pay $50 to $100 for an X-ray, she said.
Neither the U.S. Preventive Services Task Force, an independent panel of experts in medicine, nor the American Cancer Society recommend screening for lung cancer. Berg said recommendations for the U.S. task force may be available by the end of 2012.
The American Lung Association will have recommendations on lung cancer screening in about three months, said Norman Edelman, the Washington-based group's chief medical officer. “Lung cancer kills more people than any other cancer. It's a devastating disease. The cure rates are small,” he said. “We certainly need better tools to deal with lung cancer. There is a hope that catching lung cancer early will increase survivability. We need a lot more research.”