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

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

Annie Chen first noticed she was unusually short of breath in 2017, while running to catch the bus home to New Jersey from her job in Manhattan. She told her primary care doctor, thinking of her father, who died of lung cancer at 71. But her doctor told her not to worry — her father was a heavy smoker, and Ms. Chen had never smoked.

She continued to have difficulty breathing, but it wasn’t until two years later that a doctor ordered an X-ray, and Ms. Chen was diagnosed with Stage 4 lung cancer. “My whole world crashed,” she said. She was just 48, with an 11-year-old daughter, a husband who also had health issues and a mortgage to pay off.

“My family needs me,” she recalled thinking.

Ms. Chen’s case represents a confounding reality for doctors who study and treat lung cancer, the deadliest cancer in the United States. The disease’s incidence and death rates have dropped over the last few decades, thanks largely to a decline in cigarette use, but lung cancers unrelated to smoking have persisted.

The thinking used to be that smoking was “almost the only cause of lung cancer,” said Dr. Maria Teresa Landi, a senior investigator at the National Cancer Institute, which is part of the National Institutes of Health. But worldwide, roughly 10 to 25 percent of lung cancers now occur in people who have never smoked. Among certain groups of Asian and Asian American women, that share is estimated to be 50 percent or more.

These cancers are increasingly drawing the attention of researchers like Dr. Landi, who are studying the role that environmental exposures, genetic mutations or other risk factors might play. They have already found some early hints, including a clear link to air pollution.

Physicians are also testing new approaches to better detect lung cancer in nonsmokers, and trying to understand why it is more prevalent in people of Asian ancestry and women and why it is being seen among younger people.