Survival trends in extensive-stage small cell lung cancer in the pre-immunotherapy and immunotherapy eras: a population-based SEER study

Background: Extensive-stage small cell lung cancer (ES-SCLC) is a highly aggressive malignancy with limited treatment options. Immune checkpoint inhibitors (ICIs) have marked the beginning of the immunotherapy era for SCLC. However, population-level survival trends following the introduction of immunotherapy remain unclear.

Methods: We conducted a retrospective study using Surveillance, Epidemiology, and End Results (SEER) data from 2015 to 2021 to analyze survival outcomes in ES-SCLC patients before (2015–2017) and after (2019–2021) the introduction of ICIs. We employed propensity score matching (PSM) to adjust for confounding factors and used Cox regression models to identify prognostic factors. Kaplan-Meier analysis and log-rank tests were used to assess overall survival (OS) and cancer-specific survival (CSS).

Results: A total of 7,214 patients were included. After PSM, patients diagnosed in the 2019–2021 cohort demonstrated significantly improved survival compared with those diagnosed in the 2015–2017 cohort. The median overall survival (mOS) improved from 4.0 months [95% confidence interval (CI): 4.0–4.0] in the pre-immunotherapy era to 5.0 months (95% CI: 4.0–5.0) in the post-immunotherapy era [hazard ratio (HR) =0.849, 95% CI: 0.800–0.902; P<0.001], indicating that patients diagnosed during the immunotherapy era experienced better survival than those diagnosed during the pre-immunotherapy era. Marital status, geographical area, and metastasis sites were identified as significant prognostic factors. Notably, brain metastasis did not significantly affect survival, likely due to advancements in treatment.

Conclusions: Patients diagnosed during the immunotherapy era showed improved survival compared with those diagnosed during the pre-immunotherapy era. Socio-economic and geographical factors also play a critical role in prognosis, suggesting that personalized treatment strategies are essential for optimal patient outcomes.