AbstractBackgroundLung cancer patients face a high risk of thromboembolism (TE), which is considered to be a poor prognostic factor. However, the impact of symptomatic cerebral infarction (CI) and pulmonary embolism (PE) on the prognosis of advanced non‐small cell lung cancer (NSCLC) patients is not fully understood.MethodsWe retrospectively identified 46 patients with advanced NSCLC who developed symptomatic CI or PE at five hospitals in Japan between January 2010 and December 2019. Prognosis and biomarker levels after incident CI and PE were investigated.ResultsOf the 46 patients, 36 developed symptomatic CI, and 10 developed symptomatic PE. The median follow‐up duration after incident CI and PE was 18.2 months. Although the proportion of Common Terminology Criteria for Adverse Events grade 4 tended to be higher in patients with PE than in those with CI (30% vs. 11%,p= 0.16), the overall survival (OS) after incident TE tended to be worse in patients with CI than in those with PE (median 2.3 months vs. 9.1 months, log‐rank testp= 0.17). Multivariate analysis showed that OS after CI was worse in patients with high D‐dimer (DD) levels than in those with low DD levels at the time of incident CI (median 1.3 months vs. 8.3 months, log‐rankp< 0.001).ConclusionsThis retrospective study demonstrated that the prognosis of patients tended to be poorer after CI than after PE. The DD levels at the time of incident CI might be a promising predictor of clinical outcomes in advanced NSCLC patients who develop CI.