The findings also do not shed light on whether CT screening would be effective in other groups of people, such as light smokers, nonsmokers or younger people, said Richard Fagerstrom, one of the trial investigators.
"The application of these methods to a more general population may be difficult to decipher," Varmus added. "We don't yet have a recommendation for the scheduling of screening or for how many years it should be used. That will have to be left to others once the full dataset is available."
Still, advocates for lung cancer patients expressed optimism.
"Now we have validation from the NCI that screening people at high risk for lung cancer with CT scans can significantly reduce mortality in lung cancer, which is causing more deaths each year than breast, prostate, colon and pancreatic cancers combined," Laurie Fenton-Ambrose, president and CEO of Lung Cancer Alliance, said in a statement.
The larger public health message on lung cancer prevention should not be forgotten, however, Varmus added.
"No one should come away from this announcement believing that it's safe to continue to smoke or start smoking," he said. "Not smoking and quitting smoking remain the best defense against lung cancer."
There's more on the study at the U.S. National Cancer Institute.
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