Up to 25% of lung cancers now occur in people who have never smoked and most often in women, people of Asian descent, and people with a family history of lung cancer, according to the National Institutes of Health.
"Lung cancer in never-smokers is emerging as a separate disease entity with distinct molecular characteristics that directly impact treatment decisions and outcomes," Andreas Wicki, an oncologist at the University Hospital Zurich, Switzerland, told the BBC.
"When we see 30- or 35-year-olds with lung cancer, they are usually never-smokers," he said.
But the underlying factors that lead to lung cancer, which is the most common cancer worldwide, is poorly understood and being studied more now, reported The New York Times.
And they have already found some early clues — most notably, a strong connection to air pollution.
At the University of California, San Diego, a research team led by NIH's Dr. Maria Landi and Dr. Ludmil Alexandrov is studying the role that environmental exposures, genetic mutations, or other risk factors might play in never-smokers who have lung cancer.
"The scientists found that people who'd had high exposure to fine-particle air pollution, which comes from vehicles and industry, were 1.6 times more likely to have mutations in the gene for TP53, a protein that helps suppress tumors," according to the NIH report.
Solange Reyner ✉
Solange Reyner is a writer and editor for Newsmax. She has more than 15 years in the journalism industry reporting and covering news, sports and politics.