P1.12-12 Factors Affecting the Risk of Brain Metastasis in Limited-Stage Small Cell Lung Cancer After Prophylactic Cranial Irradiation

Abstract

Prophylactic cranial irradiation (PCI) can reduce brain metastases (BM) and improve overall survival (OS) in patients with limited-stage small cell lung cancer (LS-SCLC) after complete response to primary therapy. However, some SCLC patients still suffer from BM after PCI with unknown risk factors.This study conducted to assess the factors affecting the risk of BM in patients with LS-SCLC after PCI and identify characteristics of patients who may not benefit from PCI. We identified 550 patients who received chemoradiotherapy at Zhejiang Cancer Hospital in 2002–2017. All patients received PCI. Kaplan–Meier analyses and Cox regression analyses were used to identify factors influencing OS and BM. The median survival time for this patient population was 27.9 months, and the 5-year overall survival rate was 31%. Pathologic stage not only correlated with overall survival but also significantly affected the risk of BM. For the whole group, 15.6% (86/550) of the patients had evidence of metastases to brain. 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), (P=0.026), Having tumors ≥5 cm increased the 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 were significantly higher than patients ≥60 years (34.9 months VS. 24.6 months, P=0.001), however, the difference of the BM risk in two group was not statistically significant. PCI remains standard therapy after complete response to chemoradiotherapy for LS-SCLC. However, patients with tumors ≥5 cm may have a higher risk of developing brain metastases after PCI. Further work is warranted to identify patients who may not benefit from PCI.