Both smokers and non-smokers can get lung cancer, but researchers say they've found significant differences between lung cancer patients who smoke and those who don't.

While tobacco smoke has been confirmed as a known high risk factor in developing non-small cell lung cancer, or NSCLC, the disease can hit non-smokers tool, and in fact the incidence is increasing in non-smokers in many countries, the researchers note.

However, a study has found some important differences in both clinical particulars and survival rates when comparing non-smokers and smokers with NSCLC.

In a study of around 500 non-smoking Portuguese NSCLC patients and about 900 smokers diagnosed with the disease, the researchers at the Portuguese Institute of Oncology in Lisbon reported that non-smoking patients were more likely to be women.

Non-smokers were also more likely to have to most common type of NSCLC, known as adenocarcinoma, but they generally had less chronic obstructive pulmonary disease (COPD), previous cancer of the larynx, heart disease or weight loss than what was seen in smokers with lung cancer.

The survival after diagnoses was also considerable longer for non-smokers -- 51 months -- compared to 25 months for the smokers.

"In Portugal, information on the differences in the risk and survival between smokers and non-smokers with NSCLC, has been very limited up to now," says Dr. Cátia Saraiva of the Lisbon institute's Department of Pulmonology.

"Because lung cancer represents a set of tumors with confounding and sometimes misleading symptoms in both smokers and non-smokers, we felt that it was of particular importance to acquire this knowledge," she told European Respiratory Society's International Congress 2015 being held in Amsterdam, The Netherlands.

Further investigations to pursue why such differences occur -- concentrating perhaps on ageing, predisposition and lifestyle -- should help to improve diagnoses of lung cancer, Saraiva says.

"In the non-smoking group, we found professional exposure to carcinogens in 9 percent, a family history of lung cancer in 5 percent, and a previous cancer diagnosis in 6 percent. Additionally, 18 percent had high blood pressure," she explains.

Lung cancer in non-smokers is often only diagnosed in its advanced stages, when the disease has already spread into other areas of the body such as bones or the brain. This may be because non-smokers may believe themselves to be less at risk of lung cancer than smokers are, the researchers suggest.

"It seems plausible that the non-smoking Portuguese population is not aware of lung cancer risks," Saraiva says. "But we need to confirm our results through population-based studies, before public education issues can be addressed."

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