Objective To investigate the impact of the changes of posttreatment karnofsky performance status (KPSpost) on the overall survival (OS) for patients with stage Ⅳ non-small cell lung cancer (NSCLC) underwent concurrent chemoradiation.Methods A total of 279 patients (male 198 and female 81) with histological confirmed stage Ⅳ NSCLC were enrolled in this study with a median age of 58 years old (range 22 to 80 years old).There were 166 cases of squamous carcinoma,87 cases of adenocarcinoma,and 22 cases of unclassified carcinoma,respectively.All enrolled patients received more than 2 cycles of chemotherapy and more than 36 Gy of concurrent radiotherapy.Kaplan-Meier method and Log-rank test were applied to evaluate OS.Multivariate analyses were carried out by the Cox proportionalhazard model.Chi-square test and logistic regression analysis were used to explore the related factors of KPSpost.Results There were 198 patients with improved KPSpost and 81 patients with decreased KPSpost,respectively.Univariate and multivariate analyses indicated that the improvement of KPSpost was associated with longer OS.Logistic regression analysis showed that the improvement of KPSpost was positively related with treatment of more than 4-6 cycles chemotherapy concurrent with over 63 Gy radiation to primary tumor.The improvement of KPSpost also correlated positively with disease control rate (DCR),but negatively with PLT toxicity and radiation esophagitis.Conclusions KPSpost was an independent prognostic factor of OS for patients with stage Ⅳ NSCLC underwent concurrent chemoradiation.Chemotherapy of 4-6 cycles and concurrent over 63 Gy radiotherapy dose to primary tumor,as well as DCR were positive factors for KPSpost improvement.However,stage 3-4 PLT toxicities and radiation esophagitis decreased the KPSpost.