Analysis of high-risk factors for brain metastasis and prognosis after prophylactic cranial irradiation in limited-stage small cell lung cancer

Small cell lung cancer (SCLC) is an aggressive malignancy with a high propensity for brain metastases (BM). Limited-stage SCLC (LS-SCLC) can be effectively treated with chemoradiotherapy and prophylactic cranial irradiation (PCI) to enhance patient outcomes. The aim of the present study was to assess the risk factors and prognostic significance of brain metastases (BM) in patients with limited-stage small cell lung cancer (LS-SCLC) who attained complete remission (CR) or partial remission (PR) following combined chemoradiotherapy and subsequent prophylactic cranial irradiation (PCI). Data for 290 patients diagnosed with LS-SCLC and treated at Chengde Central Hospital and Hebei Cangzhou Hospital of Integrated Traditional Chinese and Western Medicine (Chengde, China), who achieved CR or PR and underwent PCI between 2015 and 2023, were retrospectively analyzed. BM rates and overall survival (OS) were estimated using the Kaplan-Meier method, whilst differences were assessed using the log-rank test. Risk factors affecting BM and OS were assessed using univariate and multivariate Cox regression analyses. The overall incidence of BM after PCI was 16.6% (48/290), with annual rates of 1.4, 6.6 and 12.8% at 1, 2 and 3 years, respectively. Multivariate Cox regression analysis identified an initial tumor size of >5 cm [hazard ratio (HR)=15.031; 95% confidence interval (CI): 5.610-40.270; P<0.001] as a significant independent risk factor for BM following PCI. The median OS was 28.8 months and the 5-year OS rate was 27.9%. The median OS for patients with and without BM at 27.55 and 32.5 months, respectively, and the corresponding 5-year OS rates were 8.3 and 31.8%, respectively (P=0.001). Median OS rates for stages I, II and III were 61.15, 48.5 and 28.4 months, respectively, with 5-year OS rates of 62.5, 47.1 and 21.6%, respectively (P<0.001). Further multivariate Cox regression analysis indicated that BM (HR=1.934; 95% CI: 1.358-2.764; P<0.001) and clinical stage (HR=1.741; 95% CI: 1.102-2.750; P=0.018; P=0.022) were significant independent risk factors associated with patient OS. In conclusion, a tumor size of >5 cm is a significant risk factor for BM following PCI in patients with LS-SCLS achieving CR or PR through radiotherapy and chemotherapy. Furthermore, BM and clinical staging independently influence OS.