Tuesday, May 23, 2006

Lung Cancer More Likely to Kill Non-Smoking Men

Lung Cancer More Likely to Kill Non-Smoking Men Study Refutes Idea That Women Are More Vulnerable
May 17, 2006 10:04:44 AM PST

Contrary to popular belief, women who have never smoked are not more likely to die of Lung cancer than men who never smoked. In fact, a new analysis by American Cancer Society researchers shows exactly the opposite is true.

The finding comes from 2 large, long-term ACS studies that included nearly a million non-smokers. Results appear in the May 17 issue of the Journal of the National Cancer Institute.

Lead researcher Michael Thun, MD, and colleagues compared lung cancer death rates among male and female non-smokers in the Cancer Prevention Study I (CPS-I) and Cancer Prevention Study II (CPS-II). The people in the 2 studies had answered questionnaires about their smoking history and other lifestyle factors when they first enrolled. The CPS-I followed participants from 1959-1972, and the CPS-II tracked participants from 1982-2000.

In both studies, lung cancer death rates were higher among men than women. In the CPS-I, the lung cancer death rate in men was nearly 19 per 100,000, but it was just 12 per 100,000 in women. That gap was narrower, but still statistically significant, in the CPS-II: 17 per 100,000 in men and 14 per 100,000 in women.

"Our findings are reassuring for women who've never smoked and who may have been alarmed by recent reports indicating their risk was higher than it actually is," said Thun, who is vice president of epidemiology and surveillance research at ACS.

Thun said there is a perception among many doctors that lung cancer is more common in non-smoking women because many of the non-smokers they see who have lung cancer are women. But that may simply be because there are 3 times as many women who have never smoked.

"Women didn't start smoking until later in the 20th century, so there are a lot more older women who've never smoked," he explained. "The risk of developing lung cancer -- like most solid tumors -- increases with age. It increases a lot faster if you're a current or former smoker, but it increases even if you've never smoked."

Lung Cancer Patients 'Shortchanged'
The issue of lung cancer in non-smokers was thrown into the spotlight earlier this year when Dana Reeve, widow of actor Christopher Reeve, died of the disease despite never having smoked. But active smoking isn't the only cause of lung cancer. People can also get this disease through exposure to secondhand smoke, asbestos, radon, and radiation therapy, among other causes.

In fact, about 10% -15% of all lung cancer deaths in the US -- between 17,000 to 26,000 each year -- are unrelated to active smoking. Of those, about 15,000 are in people who never smoked.

If all these cases of lung cancer were considered separately from smoking-related lung cancer, they would rank between 6 and 8 on the list of most common fatal cancers, Thun and his colleagues say. The study didn't find any evidence that lung cancer rates in non-smokers have changed substantially over the years.

Nevertheless, lung cancer still gets shortchanged when it comes to public attitudes and the search for cures, Thun said.

"The funding for lung cancer is small, given the burden of suffering and death that it causes, in part because of this unspoken assumption that blames the person for smoking," he said. "But the paper points out that lung cancer deaths due to factors other than smoking [constitute] a substantial burden. And then it gets shortchanged again because tobacco control gets underfunded below its contribution to suffering and death."

Differences in Whites, African-Americans
Thun's analysis also found racial differences in lung cancer deaths. African-American women who never smoked had significantly higher lung cancer death rates than white women who never smoked, and the gap got bigger between the first and second study. Rates were also higher among African-American men than white men, but there were too few black men in the first study to make the finding statistically meaningful.

Thun says these discoveries merit further research.

Lung cancer death rates have been higher among African-American men than white men since the 1960s, but most of this difference was thought to be due to different smoking patterns between the races. African-American men are a little more likely to be smokers, tend to smoke cigarettes with higher levels of tar, and tend to have higher levels of smoking-related chemicals in their blood.

The fact that this new analysis found a large difference in non-smokers, too, suggests there's more to the picture than just smoking habits.

"That is a novel finding that needs to be followed up," Thun said.

Citation: "Lung Cancer Death Rates in Lifelong Nonsmokers."Published in the May 17, 2006, Journal of the National Cancer Institute (Vol. 98, No. 10: 691-699). First author: Michael J. Thun, MD, American Cancer Society.

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