WEDNESDAY, March 19, 2003 (HealthDayNews) -- If you're a smoker -- or an ex-smoker -- the fear of lung cancer probably lurks somewhere in the back of your mind.
But have you ever wondered how likely you are to actually develop the deadly disease?
New research shows that even among long-term, heavy smokers, the risk of getting lung cancer can vary dramatically -- from less than 1 percent to a whopping 15 percent.
The risk of getting lung cancer was most heavily influenced by age, duration of smoking and how much a person smoked, says Dr. Peter Bach, lead author of the study and an epidemiologist and pulmonary physician at Memorial Sloan-Kettering Cancer Center in New York City.
"Before this study, anyone who smoked for 25 or 30 years thought that they were at extra high risk of lung cancer when, in fact, there is lots of difference in risk," Bach says.
For individual smokers, this study may either be very good news or very troubling news.
Consider: A 51-year-old woman who smoked a pack a day for 28 years and then quit has only a 0.8 percent chance of getting lung cancer in the next decade, the study found.
Compare her to a 68-year-old man who has smoked two packs a day for 50 years and refuses to stop smoking. If he keeps puffing away, his risk of getting lung cancer in the next decade is 15 percent.
The study appears in the March 19 issue of the Journal of the National Cancer Institute.
Bach and his colleagues undertook the study in part because of the increasing interest in using low-dose helical computed tomography scans, commonly called CT scans, to detect lung cancer in its early stages.
The problem with CT scans is that the test often detects lung abnormalities that aren't lung cancer, including infections and scarring. This can lead to unnecessary biopsies and needless anxiety, he says.
"We thought it would be very important for people to know if they're at the high end or the low end of the risk scale," he says. "That way, they can make a decision with their physician about whether or not these CT scans are for them."
Bach and his colleagues used previous data on more than 14,254 men and women aged 50 to 59 who were considered heavy smokers, which was defined as having smoked a pack a day for at least 20 years. The participants were either current smokers or had stopped smoking within six years before enrolling in the study. Another 4,000 participants were men aged 45 to 69 who had been exposed to asbestos, a risk factor of lung cancer, and who were current or former smokers.
Study participants were followed for 10 to 20 years. During the follow-up, about 1,110 people were diagnosed with lung cancer.
Bach and his colleagues used the data to create a mathematical model to calculate who is most likely to get lung cancer.
Researchers then applied the model to a sample of 300 people who had undergone cancer screening at the Mayo Clinic and came up with these sample profiles:
- A 51-year-old woman who smoked a pack a day for 28 years and then quit has only a 0.8 percent chance of getting lung cancer in the next decade.
- A 52-year-old woman who smoked a pack a day for 35 years and who continues to smoke has a 2.8 percent chance of getting lung cancer in the next decade.
- A 58-year-old man who smoked 25 cigarettes a day for 40 years but quit three years ago had a 4.1 percent chance of getting lung cancer in the next decade.
- A 56-year-old woman who smoked two packs a day for 44 years and continued to smoke had a 8.4 percent chance of getting lung cancer in the next decade.
- A 68-year-old man who smoked two packs a day for 50 years and refused to stop smoking had a 15 percent chance of getting lung cancer in the next decade. His risk would drop to 10.8 percent if he quit.
"At the high end, you're talking about one in seven people," he says.
Lung cancer is the leading cancer killer of both men and women, according to the American Lung Association. There were an estimated 164,100 new cases of lung cancer and an estimated 156,900 deaths from the disease in the United States in 2000.
Even if your risk of getting lung cancer is relatively low, the study should not be read as permission to keep puffing away, says Dr. Jay Brooks, chairman of hematology/oncology at the Ochsner Clinic Foundation in New Orleans.
"There is no safe level of exposure to the carcinogens in tobacco smoke," he says. "Quitting is absolutely the No. 1 thing an individual can do to reduce their risk of ever developing cancer."
About one-third of cancers in the United States are directly related to cigarette smoke, including lung, throat, sinus, esophagus, pancreas, kidney and cervical cancers, he says.
More information
Smokers can assess their risk of lung cancer using the Memorial Sloan-Kettering Cancer Center prediction tool. Or read about diagnosis and treatments at the National Cancer Institute.
