Female non-smokers no more at risk of lung cancer than males

May 17 2006

To date few studies have examined the age, sex, and race-specific risks of lung cancer incidence and death among people who have never smoked tobacco.

That information is clearly needed if the the risks associated with smoking and passive smoking are to be understood along with racial and sex disparities and trends due to factors other than active smoking.

Researchers for the American Cancer Society, in Atlanta, and the University of California, San Diego, say women who have never smoked are no more likely to die from lung cancer than male non-smokers.

In an analysis of two large American Cancer Society studies of more than 940,000 adults with no history of smoking, men who never smoked were found to have higher lung cancer death rates than female lifelong non-smokers.

The studies carried out during 1959–1972 and 1982–2000 were used to compare lung cancer death rates between men and women and between African Americans and whites, and analyzed temporal trends in lung cancer death rates among people who had never smoked across the two studies.

Dr. Michael J. Thun who led the study says the paradox is that the findings are compatible with the clinical perception that women outnumber men among lung cancer patients who never smoked, and the reason appears to be unrelated to a cancer risk.

Dr. Thun says this is because there are far more women than men over the age of 60 who never smoked.

Census data supports that figure and shows there are 16.2 million women compared to just 6.4 million men in the U.S. who are over 60 and never smoked.

The death in March of Dana Reeve of lung cancer, a non-smoker and widow of "Superman" star Christopher Reeve, galvanised attention on the small but significant risk that non-smokers have from lung cancer.

But the fact is that between 80 and 90 percent of the 174,470 new cases of lung cancer that will be diagnosed in the United States in 2006 are caused by smoking.

Lung cancer remains by far the biggest cancer killer in the world, and 162,460 deaths are predicted this year in the United States alone.

It is estimated that 15,000 lifelong non-smokers die of lung cancer every year in the U.S. caused by secondhand smoke, asbestos exposure and radon gas.

Dr. Thun says the findings will serve to reassure women who have never smoked and who may have been alarmed by recent reports indicating their risk was higher than it actually is and men overall still have a significantly higher risk of dying from lung cancer than women do.

In conclusion the researchers say that contrary to clinical perception, the lung cancer death rate is not higher in female than in males who have never smoked and there is little evidence of it having increased over time in the absence of smoking.

One surprising finding was that lung cancer mortality is higher among African American than white women who never smoked and that say the researchers warrants further investigation.

The research is published in the Journal of the National Cancer Institute.