The standard treatment for non-small cell lung cancer, stage IV or IIIB malignant pleural effusion is chemotherapy. The decision to use a regimen is currently determined by toxicity or by physician's preference. In this protocol, the treatment regimen will be assigned based on the patients' tumor molecular profile. A tumor molecular profile analysis will allow the physician to define a specific molecular portrait that shows the genetic basis of the tumor. This analysis results in a detailed report that will determine which chemotherapy will be assigned to the patient.