Many Lung Cancers Are Now in Nonsmokers. Scientists Want to Know Why.

Roughly 10 to 25% of lung cancers worldwide now occur in people who have never smoked, according to researchers at the National Cancer Institute. Among certain groups of Asian and Asian American women, that share reaches 50% or more. Scientists studying 871 nonsmokers with lung cancer from around the world found that certain DNA mutations were significantly more common in people living in areas with high air pollution levels, including Hong Kong, Taiwan and Uzbekistan.

The research, published in Nature this month, revealed that pollution both directly damages DNA and causes cells to divide more rapidly. The biology of cancer in nonsmokers differs from smoking-related cases and may require different prevention and detection strategies. Nonsmokers with lung cancer are more likely to have specific 'driver' mutations that can cause cancer, while smokers tend to accumulate many mutations over time.

Current U.S. screening guidelines recommend routine testing only for people ages 50 to 80 who smoked at least one pack daily for 20 years. Taiwan now offers screening for nonsmokers with family history after a nationwide trial detected cancer in 2.6% of participants.

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