Lung Cancer Incidence Increasing Among Nonsmokers

The incidence of non–small-cell lung cancer (NSCLC) among self-reported never-smokers appears to be increasing, according to authors of two retrospective studies presented at the 2015 World Conference on Lung Cancer in Denver, Colorado (abstracts 22.01 and 24.03).

In England, a review of 2,170 lung cancer surgery patient records at a large cancer center found that NSCLC incidence among never-smokers had increased from 13% to 28% between 2008 and 2014. The annual incidence of developing lung cancer among never-smokers climbed over that period, but most dramatically between 2013 and 2014, when never-smokers’ proportion of the lung cancer surgery population jumped from 20% to 28%.

“We observed more than double the annual incidence of never-smokers presenting with NSCLC in the last 7 years,” said coauthor Eric Lim, Royal Brompton & Harefield NHS Foundation Trust in London.

Because the Royal Brompton & Harefield NHS Foundation Trust has one of England’s largest surgical volumes for lung cancer, the authors hypothesize that their findings are representative of the United Kingdom, Dr. Lim said.

A separate review of three lung cancer databases by researchers in Texas came to a similar conclusion. Their study “demonstrates an increasing proportion of never-smoker with NSCLC between 1990 and 2013 in a large, geographically and demographically-diverse population,” reported lead study author Lorraine Pelosof, MD, PhD, of the hematology/oncology department at the University of Texas Southwestern in Dallas, Texas.

That analysis included lung cancer registry data for a total of 10,568 patients who were diagnosed with NSCLC and 1,504 patients diagnosed with small-cell lung cancer (SCLC) between 1990 and 2013 at the University of Texas Southwestern Medical Center in Dallas, Parkland Hospital in Dallas, and Vanderbilt University in Nashville, Tennessee. The trend was statistically significant even after statistically controlling for patient age and gender (P < .0001), Dr. Pelosof reported. Never-smokers diagnosed with NSCLC were significantly more likely to be female than male (65% vs 35%; P < .0001). (Dr. Lim reported that 67% of never-smokers undergoing NSCLC surgery in England were female.)

“The increase in the percentage of NSCLC never-smokers was seen at both university hospitals and the Dallas county hospital,” she noted.

The results are not likely due to ascertainment bias caused by better detection of low-stage tumors among never-smokers, Dr. Pelosof believes. “Our study looked at stage and we found that stage IV cancers was increasing,” she noted.

Lung cancer among never-smokers is recognized as a distinct entity, which is frequently diagnosed at advanced stages. “Because the biology and, thus, often the treatment options of lung cancer in never-smokers differs from that of smokers, further investigation is warranted as to the etiology of the increasing incidence of never-smoker lung cancer,” Dr. Pelosof said.

It is unclear what may be responsible for the increasing proportion of NSCLC patients who are never-smokers, noted Everett Vokes, MD, the John Ultmann professor and chair, department of medicine, University of Chicago. Possible culprits might include second-hand smoke or radon, he noted. “But those shouldn’t be increasing,” he was quick to point out. “Of course, it could be pollution in the air,” he added.

“Clearly, this research suggests that efforts need to be expanded on early detection of lung cancer in this increasing cohort without any observable risk factors,” Dr. Lim said.