Researchers have confirmed that screening heavy smokers through the use of computer tomography (CT) can detect early signs of lung cancer and reduces deaths by around 20 percent.
The study verifies and expands upon the preliminary results of the National Lung Screening Trial that were announced in November.
"It opens up the field of screening for lung cancer," said study researcher Constantine Gatsonis, a biostatistics professor at Brown University.
The new article in this week's New England Journal of Medicine gives many detailed results of the study, providing far more data on the medical aspects of the trial than the November report did. "It presents additional information and informs as to the benefits and risks of the scans," said study researcher Dr. Christine Berg, chief of the early-detection research group at the National Cancer Institute.
Researchers screened close to 55,000 participants for lung cancer either with the low-dose helical (also called spiral) CT scans or with standard chest X-rays, and followed up with them for five years. Participants ranged in age from 55 to 74 and were current or former heavy smokers with a history of at least 30 "pack-years," which researchers calculated by multiplying the number of years spent smoking by the average number of packs of cigarettes smoked per day.
Early detection can often make the difference in a cancer patient's survival, but lung cancer is particularly difficult to catch quickly. "Often by the time we find it, it has metastasized," Gatsonis said.
Of those who received a CT scan, 356 died from lung cancer over the follow-up period, compared with 443 of those in the chest X-ray group, statistically a very large difference, the study said.
Using CT scans to screen for lung cancer is not without possible problems, however. Although the helical pattern of the scanner lowers the amount of radiation required to create an image, it still bombards the body with more radiation than a traditional X-ray, and repeated screenings increase the small but real chance of damaging cells and actually causing cancer.
The lower radiation also means the image created is not always perfectly clear, often showing false signs of lung cancer that lead to unnecessary scans and biopsies.
In addition, the scan can cost hundreds of dollars. "It's expensive compared to other kinds of screening," Gatsonis said.
Should scans become routine for smokers?
Although the paper covers many detailed results of the screening trial, a great deal more awaits examination, and articles analyzing the broader effects of the study will be published in the coming months, the researchers said. The effect of the scans on participants' smoking habits, the kind of medical care they received, and the costs and benefits of the scan will be addressed.
Data from the trial also will be used to create statistical models of how CT scans could be deployed in larger and more diverse populations, and what impact such scans could have medically and economically. "It will serve as a rich resource over a long time," Berg said.
Those models could have a real effect on future medical care, the researchers said. They will be studied by groups including the U.S. Preventive Services Task Force and used to make recommendations on whether government and private insurance should cover the CT scans. "It could become a procedure similar to mammography," Berg said.
Screening is only one of many ways to reduce lung cancer risk, both Gatsonis and Berg said, and probably isn't the answer for everyone. The National Lung Screening Trial studied a high-risk population, so the radiation risks were smaller for the participants than the potential benefits were. Quitting smoking is the easiest way to lower lung cancer risks and improve health.
But for people over 55 with a long history of smoking, CT scans could be the best bet to catch lung cancer in time to do something about it. "With screening, you can really have an impact," Gatsonis said.
The screening trial was run principally by the National Cancer Institute and the American College of Radiology Imaging Network.
Pass it on: Routinely screening heavy smokers with CT scans could reduce lung cancer deaths.
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