Lung Cancer on the Rise in Nonsmokers - But Why?

The proportion of lung cancer patients who never smoked more than doubled from 2008 to 2014, a British investigator reported here.

Never-smokers accounted for 13% of non-small cell lung cancer (NSCLC) cases at the beginning of the study period and rose steadily to 28% by November 2014. Women accounted for two-thirds of the nonsmokers who developed NSCLC, which was associated with nonspecific symptoms or no symptoms in a majority of cases.

Both the percentage and absolute number of NSCLC cases involving nonsmokers increased during the study period, supporting the view that the increase is real and not an artifact created by reductions in smoking prevalence, Eric Lim, MD, of the Royal Brompton Hospital in London, reported at the World Conference on Lung Cancer.

"As this group of patients do not have established risk factors, research into early detection - ideally, by noninvasive or molecular screening - is urgently required to identify early lung cancer in nonsmokers," Lim said.

"We found that the absolute numbers are increasing in real time," he added. "But I say that with a caveat: We are starting from a position where we know the diagnosis. We really don't know the true incidence in the undiagnosed population."

Lung Cancer Risks for Non-smokers Secondhand smoke. Each year, an estimated 3,400 non-smoking adults die of lung cancer as a result of breathing secondhand smoke. Laws that ban smoking in public places have helped to reduce this danger. The American Cancer Society Cancer Action Network (ACS CAN), the nonprofit, nonpartisan advocacy affiliate of the American Cancer Society, is working to expand and strengthen these laws to further protect both smokers and non-smokers from the dangers of secondhand smoke.

Cancer-causing agents at work. For some people, the workplace is a source of exposure to carcinogens like asbestos and diesel exhaust. Work-related exposure to such cancer-causing materials has decreased in recent years, as the government and industry have taken steps to help protect workers. But the dangers are still present, and if you work around these agents, you should be careful to limit your exposure whenever possible.

A study conducted at three U.S. medical centers also showed a rising incidence of NSCLC in nonsmokers since 1990, including a two-fold increase at one of the centers. The proportion of nonsmokers among patients with small cell lung cancer (SCLC) did not change from 1990 through 2013, said Lorraine Pelosof, MD, PhD, of the University of Texas Southwestern Medical Center in Dallas.

The reasons for the increase in nonsmokers among patients with NSCLC remain unclear. Mutation analysis of tumors could help inform the issue, but detailed studies have yet to be done in nonsmokers, said Everett Vokes, MD, of the University of Chicago.