Objective:We aimed to investigate the factors affecting the complete response (CR) rate and the effect of treatment response on survival in patients with extensive stage-small cell lung cancer (ES-SCLC) who received a combination of cisplatin and etoposide as first-line therapy.Method:This retrospective analysis included 140 ES-SCLC patients, who were followed in an oncology clinic. Patients were divided into two groups as CR and non-CR according to radiological evaluation after first line chemotherapy. Clinical and demographic characteristics and pre-treatment hemogram parameters were obtained from electronic medical record system.Results:While CR was seen in 34 (24.3%) of all patients after the first line chemotherapy, 106 (75.7%) patients were in the non-CR group. On univariate analysis, predictors for CR to treatment were the absence of brain metastasis, receiving 6 chemotherapy cycles and good performance status (p