Background : Small-cell lung cancer (SCLC) presents aggressive clinical behavior, and its prognosis is still poor. Previously, performance status (PS), or the existence of brain, bone, or liver metastasis were reported to be unfavorable prognostic factors. Given the recent progress of treatment modalities such as radiotherapy techniques and bone modifying agents, the prognostic factors might be different from previous findings. Therefore, we analyzed the prognostic factors of extensive disease SCLC (ED-SCLC) in recent years. Methods : ED-SCLC patients treated in Tokushima University Hospital between 2010 and 2016 were analyzed. Log-rank test and the Cox proportional hazards regression model was used in univariate and multivariate analysis, respectively. Results : Totally, 79 patients were analyzed. In the univariate analysis, age, PS, interstitial pneumonia (IP), liver metastasis, pleural dissemination, neutrophil counts, hypoalbuminemia, hypercalcemia and several liver and biliary enzymes were identified as poor prognostic factors. In the multivariate analysis, age, PS, IP, and liver and biliary enzymes were identified. Moreover, the PS in patients with liver metastasis was significantly worsened. Conclusions : In this study, we newly demonstrated that IP was a significant poor prognostic factor of ED-SCLC. Although liver metastasis was not extracted in multivariate analysis, it may have an impact on the prognosis of ED-SCLC