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Experts Assess Lung Cancer Risk Among Smokers

New data based on age, time spent smoking

MONDAY, Nov. 29, 2004 (HealthDayNews) -- The largest study of its kind has come up with hard, cold numbers that pinpoint the risk of lung cancer for smokers and former smokers.

The International Early Lung Cancer Action Project used computed tomography (CT) scans to look for early signs of lung cancer in more than 27,700 smokers and ex-smokers. The results were presented Nov. 29 at the Radiological Society of North America's annual meeting in Chicago.

"Based on our data, we can now predict by age, by how much has been smoked or when a smoker has quit, what is the likelihood of developing lung cancer," said project leader Dr. Claudia I. Henschke, chief of chest imaging at New York-Presbyterian Hospital in New York City.

For example, her team found that 15 cases of lung cancer will be detected in every 1,000 smokers aged 50 to 74, compared to six cases per 1,000 in those under 50.

The total number of cigarettes smoked is also important. There will be 28 cases of lung cancer among 1,000 people who smoked three packs a day for 20 years or more, compared to 16 per 1,000 who smoked three packs a day for 10 to 20 years.

People who have managed to kick the habit are at risk long after they stop, Henschke noted, partly because smokers remain more likely to die suddenly of heart disease. The risk of lung cancer does not decline much until 20 years after the last cigarette has been inhaled.

The benefit of early detection of lung cancer is clear, she said. With annual screening, there is a better than 75 percent chance that detection and surgery will save a life. Without screening, the probability of a cure is no better than 10 percent, the researchers said.

But a screening test runs about $300, Henschke said, so cost enters into the decision. For example, it probably makes sense for someone under 75 to have the test, because the expected life span is more than 10 years and early detection will buy extra years. But someone over 80 is more likely to die of other causes, and therefore the benefit is less certain.

It's a decision that has to be made by each individual, preferably after consulting a doctor, Henschke said, but she acknowledges that a purely logical approach might not be easy.

"The mathematics are there, the data are there, and I hope it can be explained to people," she said.

Another speaker at the meeting described work on a computer program that might make a decision on surgery easier once a mass is detected in a lung.

Researchers at the University of Michigan Comprehensive Cancer Center are developing software that analyzes a series of CT scans to determine if a suspicious mass is cancerous or noncancerous.

Right now, a lung biopsy is necessary to obtain a tissue sample for laboratory analysis, explained Lubomir Hadjiyski, a research assistant professor of radiology at the University of Michigan Medical School. "We hope we can give correct recommendations that would decrease the number of unnecessary biopsies," he said.

Hadjiyski and his colleagues have already developed a similar program for the diagnosis of breast cancer. Clinical trials of the lung cancer program could start "in a year or two," he added.

More information

What you need to know about smoking and health is outlined by the U.S. Centers for Disease Control and Prevention.

SOURCES: Claudia I. Henschke, Ph.D., M.D., professor, radiology, New York-Presbyterian Hospital, New York City; Lubomir Hadjiyski, Ph.D., research assistant professor, radiology, University of Michigan Medical School, Ann Arbor; Nov. 28-29, 2004, presentations, Radiological Society of North America annual meeting, Chicago
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