Abstract
BACKGROUND: Combined small cell lung cancer (CSCLC) is a subtype of small cell lung cancer (SCLC) which contains both components of SCLC and non-small cell lung cancer (NSCLC). The prognostic outcomes and treatment strategy of it are still unclear. A large-scale retrospective study was performed to investigate proper treatments for CSCLC. METHODS: All cases of CSCLC were identified from the SEER database during the period of 2004-2016. Clinical characteristics, first-line treatments, surgical procedures and survival data including overall survival (OS) and cancer-specific survival (CSS) were analyzed. RESULTS: A total of 37,639 SCLC patients were identified. CSCLC accounted for 2.1% (784/37,639). The mean age of CSCLC cohort is 67.3±9.9 years old. Male and white ethnicity patients were accounted for larger proportions (55.7% and 80.4%). The oncological characteristics of CSCLC were consistent with SCLC that most of patients were diagnosed as higher grade and advanced stages. The prognosis of CSCLC was better than SCLC but worse than NSCLC in IA-IIIA stages. No difference was observed in IIIB-IV. Surgery was beneficial in IA-IB stage CSCLC. Adjuvant chemotherapy seemed to have few effects on early stage patients. Trimodality treatment could significantly improve OS in IIA-IIIA CSCLC patients. Chemotherapy-based treatment is predominant choice in advanced stage patients. CONCLUSIONS: CSCLC is a rare and special subtype of SCLC. It has better survival outcome than non-CSCLC in early stage. Surgical treatment is crucial in early stage of CSCLC. Prognostic improvement might be achieved from trimodality treatment in stage IIA-IIIA. Chemotherapy-based treatments should be considered in advanced stage. The effect of surgical treatments in advanced stage patients should be further investigated.