1789P Fewer liver and lymph node metastases may contribute to survival benefits for patients with c-SCLC compared with SCLC

Abstract

This study was mainly aimed to evaluate clinicopathological characteristics and prognosis differences between patients with combined small cell lung cancer (c-SCLC) and small cell lung cancer (SCLC). We screened a total of 400 patients diagnosed with c-SCLC and 20841 patients with SCLC between 2010 and 2015 from SEER database. The chi-square test was used to compare patient baseline characteristics differences between c-SCLC and SCLC. Propensity Score Matching (PSM) was used to eliminate any bias between patients with c-SCLC and SCLC. Logistic regression was used to identify independent risk factors for c-SCLC and SCLC patients. In addition, univariate and multivariate Cox proportional hazards regression models were used to analyze the influence of different variables on overall survival (OS). Our result revealed that the OS of c-SCLC patients was significantly better than that patients with SCLC before PSM (P < 0.001). Further multivariable analysis showed that liver metastasis (HR: 1.218; 95% CI: 0.858-1.729; P = 0.269) and lung metastasis (HR: 1.057; 95% CI: 0.729-1.534; P = 0.768) were not significant and independent factors on c-SCLC patients’ survival. Then, we conducted PSM to eliminate bias between patients with c-SCLC and SCLC. However, the result showed that there was no significant difference on OS between c-SCLC and SCLC patients after PSM (P = 0.789). Multivariate logistic regression analysis revealed that the risk of N metastasis (OR: 0.555; 95% CI: 0.439-0.703; P < 0.001) and liver metastasis (OR: 0.591; 95% CI: 0.448-0.779; P < 0.001) was lower for c-SCLC patients compared with SCLC patients. C-SCLC patients’ prognosis was better than that of SCLC patients, which may be due to fewer liver and lymph node metastases at the time of diagnosis. However, if we limited the clinical variables, there was no difference in survival between c-SCLC and SCLC patients.