RNA extraction: The investigators will extract total RNA from cell lysates by using Tri-reagent (Molecular Research Center, Inc., Cincinnati, Ohio) and an RNA Mini Kit (Qiagen, Hilden, Germany) according to the manufacturer's instruction. RNA obtained from the Mini Kit column will be eluted. The quantity and quality of the purified RNA will be evaluated using a NanoDrop ND-1000 spectrophotometer will be stored at -80 C for further mutational analyses.

Data acquisition: The investigators will record and follow participants' clinical information, including ethnicity, age, gender, smoking status, histological types, lung cancer stage (the TNM status), metastatic sites, ECOG score, CT/CXR imaging, chemotherapy or radiation treatment at the time of diagnosis of lung cancer and through the entire clinical courses. Specific marker such as TTF1, is used to ensure the diagnosis of primary lung tumor. Clinicopathologic stage assigns according to the seventh tumor-node-metastasis classification. The investigators assess the treatment responses according to the Response Evaluation Criteria in Solid Tumors (RECIST) using the unidimension method, and record the best response achieved per treatment. Treatment response, progression-free survival, and overall survival are recorded prospectively for further analysis.

Statistical analysis: All categorical variables will be analyzed with Pearson's test, except where a small size required the use of Fisher's exact test. The progression-free survival curve and overall survival will be plotted by the Kaplan-Meier method and compared by the log-rank test. Multivariate analysis for overall survival will be performed using the Cox's proportional hazards model. Two-sided p-values of less than 0.05 is considered significant. All analyses will be performed using SPSS software (version 16.0 for Windows; SPSS Inc.).