Nearly 20 percent of women who develop lung cancer have never smoked, US researchers found in a study that suggests secondhand smoke may be to blame.
The Stanford University and Northern California Cancer Centre study tracked the incidence of lung cancer among one million people aged between 40 and 79. Around eight per cent of men who are diagnosed with lung cancer have never smoked, and around 20 per cent of women.
The study is published in the Journal of Clinical Oncology.
“We can actually put numbers on it now,” said lead author Dr Heather Wakelee of Stanford University, the study’s lead author. “Before this, we could only estimate based on our own census.” The authors cautioned that they did not adjust the study for secondhand smoke exposure.
“Non-smoking-associated lung cancer is an increasingly important issue,” said co-author Ellen Chang of the Northern California Cancer Centre, “Even if only because the population of never-smokers is growing.”
Lung cancer is rare among young adults. It usually is found in people who are 50 years of age or older, with an average age at diagnosis of 60. While the incidence of the disease is decreasing among Caucasian men, it is steadily rising among African-American men, and among both Caucasian and African-American women. This change probably is due to the increase in the number of smokers in these groups. In 1987, lung cancer replaced breast cancer as the number one cancer killer among women.