A smaller study published last year in the Journal of the American Medical Association concluded that CT might catch some early-stage cancers, but fast-moving, late-stage cancers rarely showed up early enough to cure - at times even appearing and killing between annual scans.
"CT screening for lung cancer should be considered an experimental procedure, based on an uncorroborated premise," the authors wrote.
To definitively answer the question, the National Cancer Institute is sponsoring a $200 million, 55,000-participant National Lung Screening Trial.
Half of the volunteers got three annual CT scans; the other half got chest X-rays. Those who urge caution say they are waiting for the NLST results.
"The right thing to do is to show it does or does not work before we promote it to the public," said Edward F. Patz Jr., a radiologist at Duke University Medical Center who is part of the NLST. "We don't know that it actually helps anybody."
What is known is that screening finds more cancer - and more lesions and nodules that might or might not be cancer - spots that doctors sometimes don't know how to treat, or whether to treat them at all.
"One negative is, we find a lot of stuff," said Dr. William C. Waterfield, a medical oncologist at Franklin Square Hospital Center in Essex, which conducted free lung screenings for about a year and now charges $100. "About 2 percent of patients will have lung cancer. Twenty-five percent and maybe higher will have abnormal CAT scans."
Those with abnormal scans are closely monitored and sometimes go through further tests, including needle biopsies, which can lead to surgery. Sometimes, patients return in a few months for repeat scans.
Doctors in Waterfield's hospital are split on the issue, but with so many smokers in the area's blue-collar community and such high rates of lung cancer, he isn't willing to wait.
Dr. Frederic W. Grannis, a thoracic surgeon at City of Hope Hospital near Los Angeles, is an investigator with the I-ELCAP. He notes only 15 percent of patients are alive five years after diagnosis.
"Despite all the potential problems with screening, in the long run it's far better than what we're doing," he said.
Those who take a wait-and-see approach are concerned about the costs of lung screening - and not just the direct ones. They worry that some hospitals are luring in patients who pay next to nothing for the scan, but then charge insurance companies for the expensive and sometimes unnecessary follow-up tests. Some critics refer to a lung scan as a "loss leader" for hospitals.
