Differences in the Presentation, Outcome and Response to Treatment Between Never- Smokers and Smokers With Non- Small Cell Lung Cancer.

Lung cancer is the most lethal of all malignant tumors affecting humans. In the United States alone an estimated 160,440 patients died of lung cancer 2004[1]. It is well known that tobacco smoking is a major risk factor and accounts for the majority of all lung cancer cases. But there is a sub group of patients with lung cancer who have never actively smoked tobacco. This group exhibits certain unique characteristics which separates them from lung cancer in smokers. It has been shown that never- smokers with adenocarcinoma have better outcomes in terms of overall survival as well as lung cancer specific survival when compared to current smokers with adenocarcinoma of the lung[2]. Also patients who are current smokers at diagnosis have decreased survival when compared to people who quit smoking[3]. The improved survival in never smokers could be due to several reasons. Such as increased incidence of co-morbid factors in smokers as result of exposure to tobacco smoke, differences in metabolism of chemotherapeutic agents or a reflection of differences in the underlying molecular biology of the tumor.

It has been demonstrated that chromosomal abnormalities are common in lung cancer patients with a smoking history when compared to never- smokers[4]. Gene mutations such as p53 mutations are more frequent in never- smokers than in previous smokers[5]. In addition mutations that are specific only to lung cancer in never smokers have been discovered, demonstrating the possibility of a separate or overlapping carcinogenesis pathway for lung cancer in never smokers vs. smokers [6].