Factors Affecting the Risk of Brain Metastasis in Limited-Stage Small Cell Lung Cancer After Prophylactic Cranial Irradiation.

Background: Prophylactic cranial irradiation (PCI) can reduce the risk of brain metastases (BM) and improve overall survival (OS) in patients with limited-stage small cell lung cancer (LS-SCLC) after partial or complete response to primary therapy. However, some SCLC patients still develop BM after PCI. This study aimed to evaluate the risk factors of BM in patients with LS-SCLC after PCI and identify characteristics of patients who may not benefit from PCI. Methods and Materials: We identified 550 patients with LS-SCLC who received chemoradiotherapy at Zhejiang Cancer Hospital between 2002 and 2017. All patients received PCI. Kaplan-Meier analyses and Cox regression analyses were used to identify factors affecting OS and brain metastasis-free survival (BMFS). Results: For this patient population, the median survival time was 27.9 months, and the 5-year OS rate was 31%. The median survival time was 24.9 months (95% CI: 22.6-27.2 months), and 30.2 months (95% CI: 24.2-36.3 months) in patients with or without BM (P = 0.000). The overall BM rate was 15.6% (86/550). The frequency of BM in patients with pathologic stages I, II, and III were 9.3% (4/43), 13.4% (7/52), and 16.5% (75/455). The patients with tumors ≥5 cm had an increased risk of BM (HR: 1.781, 95% CI: 1.044-3.039, P = 0.034) but not death (HR: 1.126, 95% CI: 0.925-1.663, P = 0.182). The median survival time among patients <60 years was significantly longer than patients ≥60 years (34.9 months vs 24.6 months, P = 0.001); however, the difference in the BM risk between the two groups was not statistically significant. Conclusion: PCI remains the standard of care for LS-SCLC patients who achieve complete or partial response after completion of chemoradiotherapy. However, patients with tumors ≥5 cm may have a higher risk of developing BM after PCI.