Clinical features and prognostic factors of IV combined small cell lung cancer: A propensity score matching analysis.

Background: Nowadays, the characteristics and treatment of combined small-cell lung carcinoma (CSCLC) remain controversial. This study aimed to analyze the features of clinical demographics, survival outcomes and treatment modalities among IV CSCLC, IV SCLC and IV NSCLC, to provide more evidence for the study of IV CSCLC.

Methods: All CSCLC, SCLC and NSCLC patient data were obtained from the SEER database (2010-2020). Pearson's χ2 test was used to compare the differences in clinical characteristics. Propensity score matching (PSM) was utilized to balance the bias of the variables between patients. Univariate and multivariate Cox proportional hazards regression analyses were performed to identify prognostic factors. KM analysis was used to calculate survival. Adjusted analyses for the primary outcome of different treatment modalities of IV CSCLC, IV SCLC and IV NSCLC were performed using Cox regression models.

Results: A total of 493 patients with IV CSCLC, 35503 patients with SCLC, 122807 patients with IV NSCLC were included in this study. The demographic characteristics and tumor characteristics of the three groups were different. Before PSM, there were significant differences in OS and CSS among IV CSCLC, IV SCLC and IV NSCLC, After PSM, there was a significant difference in OS and CSS between the IV CSCLC and IV NSCLC. Risk/protective factors for OS and CSS were different in three groups. Chemotherapy, radiotherapy, and surgery can improve IV CSCLC's survival time. The combination of surgery and chemoradiotherapy treatment group for patients with IV CSCLC demonstrated best OS compared to control treatment groups, and the surgery combined chemotherapy treatment group exhibited the best CSS. Additionally, for select patients with stage IV CSCLC who have missed the window for surgical intervention at the time of initial diagnosis, chemoradiotherapy presents a viable and effective treatment option.

Conclusions: The clinical characteristics IV CSCLC, IV SCLC and IV NSCLC were significantly different. The prognosis for IV CSCLC is notably poorer than IV NSCLC, similar to IV SCLC. Surgery combined therapy emerged as the preferred treatment modalities and chemoradiotherapy was a good choice for patients who have lost the indication of surgery for patients diagnosed with IV CSCLC.