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Women have twice the risk of developing lung cancer from smoking as men, according to a study by a physician-scientist from NewYork-Presbyterian Hospital/Weill Cornell Medical Center. The study results, which are based on an analysis of two patient populations and 10 years of National Institutes of Health-supported research using computed tomography (CT) screening, may indicate a need for increased anti-smoking efforts directed at girls and women, the study's authors say. The study appears in the January issue of the journal Lung Cancer.

Based on data from the Early Lung Cancer Action Project (ELCAP) baseline CT screenings, 22 cases of lung cancer were diagnosed in the 459 women and 8 in the 541 men enrolled in the study. Analysis of a second CT-screened population found 23 cases among 743 women and 12 among the 747 men. After using regression analysis to adjust for differences in age and the particulars of smoking history in both studies, women were 2.7 times more likely than men to have lung cancer (with a 95 percent confidence interval of 1.6 to 4.7).

"We found that women had more than twice the risk of developing lung cancer as men of the same age who smoked the same amount," says Dr. Claudia Henschke, principal investigator of the study and Professor of Radiology at Weill Cornell Medical College and Division Chief of Chest Imaging at New York-Presbyterian Hospital/Weill Cornell Medical Center. Dr. Olli S. Miettinen, Adjunct Research Professor of Medicine at Weill Cornell Medical College and Professor of Epidemiology, Biostatistics, and Occupational Health at McGill University co-authored the study.

"These results may indicate a need for increased anti-smoking efforts directed at girls and women," adds Dr. Henschke, who is also an Attending Radiologist at New York-Presbyterian/Weill Cornell. "Additionally, it would make sense to screen women at an earlier age."

"There are no clear reasons as of yet why women are at increased risk," says Dr. Henschke. Epidemiological evidence from previous cohort studies substantially contradicts the idea that women may be more susceptible to tobacco carcinogens, although the increased risk for women has been suggested in some studies. Theories—such as the underreporting of smoking by women and differential aggressiveness of cancer—that seek to explain the current study's findings are considered untenable by the authors.

The study followed 2,957 men and women age 40 and older with a history of cigarette smoking to determine which risk factors (age, gender, and number of years smoking), when combined with the size and texture of lung nodules found on CT scans, impacted the probability of developing lung cancer.

In March 2001, the Surgeon General noted that smoking-related diseases have become "epidemic" among women, with almost four out of 10 smoking-related deaths now occurring in women. This figure has more than doubled since 1965, largely due to the disproportionate rise in lung cancer mortality among women.

Lung cancer is the leading cause of cancer death among men and women, according to the American Cancer Society (ACS). In 2003, ACS estimates that 171,900 new cases of lung cancer have been diagnosed (91,800 men and 80,100 women) and that 157,200 people have died from it. Since 1987, more women have died annually from lung cancer than breast cancer, according to ACS.

The study was supported by grants from the National Institutes of Health, the Eastman-Kodak Corporation, and the General Electric Corporation.