Lung cancer is the leading cause of cancer death worldwide. Although the low 5-year survival rate (15%) has changed minimally in the last 25 years, new agents are being identified to improve results. The poor outcome is attributable to the fact that almost two thirds of cases are diagnosed when locoregional and/or metastatic extension has already occurred (1). A sensitive detection method could help early diagnosis and improve survival of lung cancer patients. With the introduction of PCR-based technologies in 1980s and refinements thereof, numerous molecular and biological markers on lung cancer tissues and exfoliated cancer cells have been investigated (2). However, evaluation of most of these transcripts, also known as biomarkers, often requires invasive procedures, such as bronchoscopy, to obtain tumor specimens. Obtaining tumor tissue may not always be logistically possible, thus preventing serial assessment during cancer progression or treatment.
