Non-smoker lung cancer rates higher than previously thought
The rate of lung cancer among people who have never smoked is higher than previously thought, a US study has found, with rates among women higher than among men.
The study also showed that lung cancer rates amongst smokers were 30 times higher than in non-smokers.
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.
"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 one of the most aggressive forms of the disease, and because it is often only diagnosed when it has reached an advanced stage, it can be very difficult to treat.
The study is published in the Journal of Clinical Oncology.