e20572 Background: We performed a large-scale, retrospective, nationwide, cohort study of the incidence of brain metastasis in patients with advanced non-small-cell lung cancer (NSCLC) according to the systemic treatment administered. Methods: The data were extracted from the Health Insurance Review and Assessment Service of Korea database from January 1, 2011 to November 30, 2016. Of the 29,224 patients newly diagnosed with stage IIIB or IV NSCLC who received first-line cytotoxic chemotherapy (CC group) or targeted therapy (TT group), 22,508 patients without brain metastasis were analyzed. Results: In total, 1,131 (5.0%) patients subsequently developed brain metastasis. The overall cumulative incidence of brain metastasis was significantly higher in the TT group than in the CC group (1-year cumulative incidence: 8.7 ± 0.6% vs. 3.8 ± 0.3%; 3-year: 17.2 ± 0.7% vs. 5.0 ± 0.3%, respectively; P < 0.001), despite the higher rate of brain metastasis in the CC group at < 3 years after diagnosis. Younger age, female sex, living in a rural area, anticoagulant use, and first-line TT (relative risk, 2.17 ± 0.03; 95% confidence interval, 1.92–2.50, P < 0.0001) retained significant associations with subsequent brain metastasis after adjusting for all variables. Conclusions: In the Korean population, the overall cumulative incidence of brain metastasis was significantly higher in patients in the TT group than in those in the CC group; the former could be regarded as having mutations in the EGFR or ALK gene.
163: Cumulative Incidence of Brain Metastasis after Diagnosis of Non-Small Cell Lung Cancer: Estimates from a Regional Cancer Centre Cohort