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Research Shows CT Scans Can Reduce Lung Cancer Deaths

November 5, 2010 at 12:00 AM EDT
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A National Cancer Institute trial found that screening by 3-dimensional X-ray tests known as "spiral CT scans" reduced lung cancer deaths by 20 percent over five years. But the test has its drawbacks, including increased exposure to radiation and false positives. Ray Suarez talks to NCI's Harold Varmus about the research.

JUDY WOODRUFF: Next: screening for lung cancer.Ray Suarez has that story.

RAY SUAREZ: Detecting cancer early can mean the difference between life and death.But there’s never been an effective early screening test for lung cancer, the deadliest of all cancers.Findings from a new study could change that.

The National Cancer Institute trial found that screening by three-dimensional X-rays called spiral C.T. scans reduced deaths from lung cancer by 20 percent over just five years.The spiral C.T. scan provides detailed pictures of the lung at various angles, and can spot growths when they’re about half the size that a regular chest X-ray can see.

The study tracked over 53,000 current and former smokers who had at least a pack-a-day habit.For every 300 people screened, one death was prevented.Lung cancer currently strikes more than 196,000 Americans a year, and kills more than 159,000, more than breast, colorectal, pancreatic and prostate cancers combined.Today, I spoke with Dr. Harold Varmus, who directs the National Cancer Institute, which funded the study.

Well, Dr. Varmus, welcome back to the NewsHour.

DR. HAROLD VARMUS, director, National Cancer Institute:Thank you very much.

RAY SUAREZ: Well, you’ve taken a very long-known disease and a fairly new diagnostic tool.What’s the significance of what you found?

DR. HAROLD VARMUS: For the first time, we have a way to reduce the risk of dying of lung cancer, at least among high-risk individuals, people who have smoked for many years and are still smoking or who have given it up in the last several years, and they are in an older age group.

And we have shown that, if we use a specialized X-ray screening device called low-dose helical C.T., computerized tomography, screening, that we can reduce the mortality caused by lung cancer in that group by 20 percent.

RAY SUAREZ: How many fewer people died in that group of high-risk people?These were already people who were at high risk for lung cancer.

DR. HAROLD VARMUS: Well, they are at high-risk, but they were all healthy to begin with.They were between 55 and 74 years of age.They had smoked an average of at least a pack a day for 30 years.

And, in that group, when half a group was randomly assigned to receive conventional chest X-ray, and that group was compared to the other half who received the helical C.T. scanning, there were roughly 500 deaths — almost 500 — in the group screened by conventional chest X-ray, and about 100 less in those who were screened by helical C.T.

It’s very important that people who are listening understand that this is far from complete protection.The screening doesn’t really prevent cancer.It detects it, presumably early, and prevents death for some people.But this is by no means a reason to retreat from our goal of getting people to stop smoking and keeping them from starting.

RAY SUAREZ: We’re talking about a fairly large number of Americans, aren’t we?

DR. HAROLD VARMUS: We are, exactly.And, of course, there are costs to this.

We don’t know exactly what the screening cost will be, but it’s going to be in the range of a few hundred dollars. Right now, the screening procedure is not covered by most insurance companies or by Medicare.

And one has to remember that it’s not just the simple screening that can cause costs.This is a very sensitive device, and it sees a lot of things that are not ultimately cancer.Roughly a quarter of people who were in this study and screened with low-dose helical C.T. scanning had some kind of positive finding, but only a small minority of those people actually had cancer.

RAY SUAREZ: So, how do you put that into the mix, the false positives, the added costs and added stress of interventions for people who haven’t developed lung cancer?

DR. HAROLD VARMUS: Well, you put it into the mix by saying, on the good side, by going through this process, we can prevent 20 percent of lung cancer deaths.That’s a big advantage.

The disadvantages are cost, emotional stress, the — going through — there are sometimes complications of doing a biopsy or doing lung surgery.And one has to weigh those things, just as you do for mammography, or for colonoscopy, for any other screening device.There are upsides and downsides, which makes this a very important public health problem.

RAY SUAREZ: How do we factor in exposing that many more people to X-rays in order to find out whether they have developed cancer or not?

DR. HAROLD VARMUS: Yes.And I’m glad you brought that up, because one of the downsides of this kind of procedure, as in mammography, is exposure to radiation.

The dosage that is received from the original — the initial screening test is relatively low.Depending on how many screening procedures one undergoes in a lifetime, the risk of inducing a cancer because of radiation exposure has to be measured and weighed against the advantages of doing so.

Obviously, if you’re at high risk of lung cancer, the advantages of being screened are more likely to outweigh the disadvantages of being exposed to radiation and having other factors weigh in.

RAY SUAREZ: Dr. Harold Varmus, thanks for talking with us.

DR. HAROLD VARMUS: My pleasure.