aHR adjusted hazard ratio CCI Charlson Comorbidity Index CI confidence interval CTx chemotherapy DM diabetes mellitus HR hazard ratio HTN hypertension ICD-10 International Classification of Diseases, Tenth Revision KCCR Korean Central Cancer Registry KNHIS Korean National Health Insurance Service Ref reference category RTx radiotherapy SEER Surveillance, Epidemiology, and End Results 1 Introduction Cancer remains the leading cause of death in South Korea, and among all cancers, lung cancer...