Prognostic Factors, Treatment, and Outcomes in Combined Small Cell Lung Cancer: a SEER Survey from 2004 to 2015

Background: The epidemiological characteristics of combined small cell lung cancer (C-SCLC) are still unclear. Therefore, in this study, we aimed to investigate the prognostic factors and treatment modalities for C-SCLC. Methods: The clinical data from patients with primary C-SCLC from 2004 to 2015 were extracted from the Surveillance, Epidemiology, and End Results (SEER) database. Next, we applied the 8th edition of the TNM classification. A Cox regression model was used to identify the relevant variables and treatment modalities which affected the overall survival (OS) and cancer-specific survival (CSS). Results: In total, 1,010 patients were included in the analysis. The median OS and median CSS were 9 months and 10 months, respectively. Individuals aged 65 and younger, female, and classified as being in an earlier stage were independent predictors of an improved OS and CSS. For patients with stage I, surgery alone significantly improved the OS (HR, 0.371; 95% CI, 0.180-0.769) and CSS (HR, 0.367; 95% CI, 0.162-0.892). For patients with stage II, surgery combined with radiotherapy significantly improved the OS (HR, 0.237; 95% CI, 0.063-0.890). For patients with stage III, radiotherapy alone was an independent predictor of OS (HR, 0.464; 95% CI, 0.316-0.618) and CSS (HR, 0.452; 95% CI, 0.305-0.670). For patients with stage IV, surgery combined with radiotherapy significantly improved OS (HR, 0.315; 95% CI, 0.181-0.547) and CSS (HR, 0.329; 95% CI, 0.189-0.573), and surgery alone also improved OS (HR, 0.257; 95% CI, 0.144-0.461) and CSS (HR, 0.280; 95% CI, 0.156-0.501). Undergoing chemotherapy was also an independent predictor of an improved OS (HR, 0.619; 95% CI, 0.419-0.915) in patients with stage III, and OS (HR, 0.283; 95% CI, 0.228-0.350) and CSS (HR, 0.289; 95% CI, 0.232-0.259) of patients with stage IV. Conclusions: These findings may help to determine possible treatment choices and aid further research on this rare disease.