An individual smoker’s risk for lung cancer can be predicted from age, sex, and smoking history, enabling patients to decide whether screening with techniques such as low-dose helical computed tomography is advisable for them, according to an article in the March 19th issue of the Journal of the National Cancer Institute.

American researchers analyzed data from a lung cancer prevention study and found that the risk for cancer can be accurately predicted based on a person's age, sex, and smoking history. These factors accounted for an individual's 10-year risk for developing lung cancer, with risks in the study ranging from a low of less than 1 percent to a high of 16 percent. The published article includes an interactive risk prediction tool.

"The risk assessment tool should help physicians and patients balance the possible risks and benefits of screening," explained Peter Bach, M.D., the lead author of the study. "For example, the subjects in our study who were at the low end of risk had less than a 1 percent chance of getting lung cancer in the next 10 years. That needs to be contrasted with the 30 to 50 percent risk that a screening computed tomogram will show some lung scar or shadow that requires further evaluation or surgical biopsy, even though it will ultimately be deemed to be harmless."

The current study was based on analysis of information from a lung cancer prevention trial called the Carotene and Retinol Efficacy Trial, a randomized, multi-center trial that examined the effect of beta-carotene and Vitamin A supplements on lung cancer prevention in 18,314 people.

The subjects included 14,254 men and women ages 50 to 69 years who were considered heavy smokers, defined as a person who had smoked at least 1 pack per day for 20 years and who was either a current smoker or had stopped smoking within 6 years prior to enrollment in the study. The remaining 4,060 participants were asbestos-exposed men ages 45 to 69 years who were either current smokers or former smokers who had quit within 15 years of enrollment. The trial was terminated in 1996 after preliminary results indicated no benefit and possible harm from the supplements for the individuals who continued to smoke.

In the new research, data from 18,172 subjects in the trial who had a history of current or former smoking were used to create a mathematical model that predicts the likelihood that an individual will be diagnosed with lung cancer within the next 10 years.

For the risk prediction model, the duration of smoking, average number of cigarettes smoked per day, duration of abstinence, and age were shown to be the main factors that determined the probability of a diagnosis of lung cancer. For example, a 51-year-old woman who smoked 1 pack per day for 29 years but stopped smoking 9 years earlier had a 0.8 percent risk for lung cancer in the next 10 years, whereas a 68-year-old man who smoked 2 packs per day for the past 50 years and continued to smoke had a 15 percent risk for developing the disease over the same 10-year period.

"Our findings suggest that accurate risk prediction may also be useful for researchers designing clinical trials of early lung cancer diagnosis," said Colin Begg, Ph.D., senior author of the study. "For example, focusing on the truly high-risk individuals may allow for more effective clinical trials of lung cancer screening and prevention."

Mark G. Kris, M.D., a coauthor, believes the new model will be a valuable tool in assessing risk. "Using the new model, we have a much better way to predict who is at high risk for developing lung cancer and, equally important, who is at a lower risk. With more than 90 million current and former smokers in the U.S., we need an accurate way to identify those individuals at exceptionally high risk who have the most to gain from screening."

The prediction tool can be found at the web site for the Memorial Sloane Kettering Cancer Center, http://www.mskcc.org/PredictionTools/LungCancer . It only applies to individuals who are older than 50 years and have smoked for at least 25 years.