The patients with lung cancer underwent PET studies with 18F-FDG and 18F-FMT before and after radio-/chemotherapy. The investigators used the ratio of the SUVmax of the mediastinal (N2) lymph node to the SUVmax of the primary tumor (N/P ratio ). All patients were divided into two groups of N/P ratio<1 and N/P ratio≥1, and the survival time was estimated by Kaplan-Meier method.