Radiation pneumonitis is the main dose-limiting toxicity of thoracic radiotherapy, which can affect life quality, survival, and the tumor-controlling effects of patients receiving thoracic radiotherapy. The purpose of this study is to: * Identify biomarkers including serum proteins, gene expression, genetic changes, and epigenetic modifications that determine radiation pneumonitis. * Investigate the relationship between radiation pneumonitis and other toxicities induced by radiotherapy. * Construct a predictive model for radiation pneumonitis. * Evaluate survival and treatment outcome of patients with radiation pneumonitis.