This is a cooperative research project involving patients on the Thoracic Oncology Service at Memorial Sloan-Kettering Cancer Center, and the laboratory of Dr. Peter Danenberg, Professor of Biochemistry and Molecular Biology, University of Southern California / Norris Comprehensive Cancer Center in Los Angeles, California. The primary objectives are to measure the proportion of patients with advanced (stage III-IV) lung cancer with methylated genes in their blood, and to determine if response to chemotherapy (complete or partial radiologic response) in patients with advanced lung cancer renders methylated genes undetectable in the blood. This research project will enroll approximately 80 patients per year over 4 years to generate a sample size of approximately 320 patients.Blood will be collected from participating patients at baseline, as close as possible to the date of their baseline radiologic assessment. Three follow-up blood collections will be drawn, each within 7-10 days of each follow-up radiologic evaluation.