In addition to reducing lung cancer deaths, CT screening also reduced deaths from any cause by 7%. The long-awaited findings, released Thursday, are regarded as a significant advance in cancer detection. According to the L.A. Times:

The results of the study among more than 53,000 former and current heavy smokers were so conclusive that the study was terminated prematurely last week and letters were sent to all the participants advising them of the results.

The findings are considered to be a major step forward in fighting lung cancer, which is expected to kill an estimated 157,000 Americans this year, because chest X-rays have never been shown to be an effective tool for identifying tumors.

“This is the first clear demonstration that a screening procedure can be effective in reducing deaths from lung cancer,” Dr. Douglas Lowy of the National Cancer Institute, which sponsored the $250-million study, said at a news conference.

Although CT screening holds the potential to save thousands of lives by catching tumors in early, treatable stages, widespread screening of the at-risk population in the U.S. — more than 80 million current and former smokers — would come at huge cost. It would also inevitably raise the risk of false-positive results, which would lead to further tests and invasive procedures in people who don’t need them.

In addition, CT scans expose patients to radiation, significantly more than standard X-rays do, and cumulative exposure over years of screening may increase people’s risk of developing other cancers. It is not clear whether the potential benefits of such screening may outweigh its risks over the long term. (More on Time.com: Radiation May Be a Greater Cancer Risk for Adults Than Doctors Thought)

For more information, please go to CNN Health. Read the full study, published in Radiology, here. Read the National Cancer Institute press release here.