Women Smokers Twice as Likely as Men to Develop Lung Cancer

Zosia Chustecka

July 11, 2006

July 11, 2006 — A study following nearly 17,000 smokers has shown that women are twice as likely as men to develop lung cancer, suggesting that they have an increased susceptibility to tobacco carcinogens. However, the study also found that once they develop lung cancer, women are more likely to survive than men, a finding that confirms previous reports.

Conducted by the International Early Lung Cancer Action Program investigators, the study appears in the July 12 issue of the Journal of the American Medical Association.

"The findings highlight the need to educate young women that they are at higher risk of developing lung cancer, even when they're smoking the same amount as men," said lead investigator Claudia Henschke, MD, PhD, from New York-Presbyterian Hospital/Weill Cornell Medical Center, New York City. "Based on their excess vulnerability to tobacco smoke, women may also need to get screened for lung cancer earlier than men," she said, suggesting that the screening threshold for women should be about 50 pack-years lower than for men.

No Symptoms, Voluntary Scanning

The researchers collected data from individuals who underwent computed tomography (CT) screening for lung cancer at centers across North America. All the participants were current or former smokers, aged 40 years or more, and had no symptoms of lung cancer at the time of screening.

The scans detected lung cancer in 156 of 7498 women (2%) and in 113 of 9427 men (1.2%). After adjustment for differences in age and smoking history, women were found to have almost twice the risk of lung cancer compared with men (odds ratio, 1.9; 95% confidence interval [CI], 1.5–2.5).

Women who were diagnosed as having lung cancer were of a similar age to the men (67 vs 68 years) but had smoked considerably less (47 vs 64 pack-years), the researchers comment. Also, women were more frequently diagnosed as having clinical stage 1 disease (89% vs 80%) and were more likely to have adenocarcinoma (73% vs 59%; P = .01).

However, women were more likely than men to survive. The hazard ratio for fatal outcome from lung cancer was 0.48 (95% CI, 0.25–0.89) after researchers controlled for pack-years of smoking, disease stage, tumor cell type, and resection.

"This clears up some of the long-standing confusion surrounding gender and lung cancer," Dr. Henschke told reporters. "Yes, given the same exposure, women are less likely to die from lung cancer than men, but they also have double the risk of getting the disease.

"We're not really sure why that might be," she added. "Is the women's cancer just less aggressive? Or is it more curable? We just don't know, but it's certainly an area that deserves more research."

Findings Are Provocative

"The findings of this important study with regard to female susceptibility are provocative," comments an accompanying editorial by Alfred Neugut, MD, and Judith Jacobson, DrPH, both from Columbia University, New York City. However, they point out that the study was screening-based and so may have had an overdiagnosis bias. The study participants had volunteered for an expensive and experimental screening procedure that is not covered by medical insurance, they note.

The finding that women have better survival from lung cancer has been documented previously, the editorialists note, and is worth studying further, they suggest. "An effort to understand the tumor and host factors that underlie the female survival advantage in lung cancer could potentially yield major benefits for the treatment of both sexes."

JAMA. 2006; 296:180-184, 218-219