Risk factors for brain metastasis in patients with small cell lung cancer without prophylactic cranial irradiation

Background This study aimed to determine the risk factors for brain metastasis (BM) and the prognostic factors for overall survival (OS) in patients with small cell lung cancer without prophylactic cranial irradiation (PCI). Patients and methods Limited stage small cell lung cancer (LS-SCLC) patients achieving a complete response (CR) or partial response (PR) were enrolled into this study between January 2010 and December 2016. We retrospectively evaluated the influencing factors for time to BM and overall survival (OS). Results A total of 153 patients were enrolled into this study. Sixty-eight developed BM during the follow-up period. For the whole cohort, the 1‑ and 2‑year BM rates were 29.4 and 41.2%, respectively. Multivariate analysis showed that T stage (hazard ratio [HR] = 2.27, P = 0.024), neutrophil-to-lymphocyte ratio (NLR; HR = 2.07, P = 0.029), time to thoracic radiotherapy (HR = 0.34, P = 0.002) and chemotherapy cycles (HR = 0.49, P = 0.036) were the independent influencing factors of time to BM. Only NLR (HR = 2.11, P = 0.005) and time to thoracic radiotherapy (HR = 1.95, P = 0.011) were independent prognostic factors of OS. Of the 68 patients developing BM, those with BM occurring as the first relapse (42/68) had better OS than the others (39.5 months vs 23.0 months, P = 0.016). Conclusion LS-SCLC patients without PCI had a high risk of BM. High T stage, high NLR, early thoracic radiotherapy and fewer chemotherapy cycles were the risk factors of BM. Further research is needed to confirm the results.