There has been an increase in the number of non-smokers being diagnosed with non-small cell lung cancer, according to new findings.
The report, which will be presented today at the European Respiratory Society's Annual Congress in Vienna, also found an increase in the number of women being diagnosed with the condition.
Little is known about risk factors that can cause lung cancer in non-smokers, although recently the World Health Organization (WHO) confirmed earlier this year that exhaust fumes from diesel engines were a cause of lung cancer.
Over the last decade, the management of lung cancer has changed considerably with new drugs and new diagnostic techniques being used. Researchers from the French College of General Hospital Respiratory Physicians aimed to examine the effect of these changes and understand the incidence and effects of lung cancer amongst the population.
They studied 7,610 people with lung cancer and 7,610 new cases of lung cancer in France in 2010; 6,083 had non-small cell lung cancer. The study follows on from a similar investigation in 2000, which also examined the characteristics of new cases of lung cancer.
Researchers collected background information on each patient, including age, smoking history, the histology of their cancer, which involves analysing tissue to understand variations in the disease, and the stage of their lung cancer upon diagnosis.
The results found an increase in the number of women and non-smokers developing lung cancer. 11.9% of the lung cancer cases in the study were non-smokers, which had also increased from 7.9% from 10 years previously. 24.4% of lung cancer patients in the 2010 study were female; an increase from 16% in 2000. When looking at the female smokers or former-smokers in the study, lung cancer rates had barely changed from 64% in 2000 to 66% in 2010. This figure had decreased in men, in addition to the rate of male never-smokers also increasing.
Additionally, the study also found that 58% of people with lung cancer were diagnosed at stage 4 of the disease. This is the most advanced stage of the disease, when the cancer has spread to both lungs, or another part of the body. This marks an increase of 15 percentage points from 43% in 2000, although authors believe this could be due to a new classification of the different stages of the disease. The study also found a change in the type of lung cancer with an increase in the number of people developing adenocarcinoma from 35.8% to 53.5%.
Lead author, Dr Chrystèle Locher, said: "We have seen from these results the change in lung cancer over the last 10 years. Not only has there been an increase in the number of women and non-smokers contracting the disease, but there has also been an increase in the number of cases diagnosed in stage 4 of the illness.
"We recently saw that the WHO have classified diesel fumes as carcinogenic, but more research is needed to understand other factors that could contribute to lung cancer in non-smokers. Anti-smoking campaigns must also target women more specifically, as we can see little change in lung cancer rates caused by smoking in women.
"It is also important to note changes in the type of lung cancer. The prevalence of cases of adenocarcinoma lung cancer is growing and further research is needed to understand the characteristics of this form of the disease."