Risk factors for brain metastases in locally advanced non-small cell lung cancer patients treated with radical radiotherapy

Background: Brain metastases (BM) happen frequently in lung cancer patients and lead to a poor prognosis as well as a lower quality of life. The aim of this study was to identify risk factors for BM in locally advanced non-small cell lung cancer (LA-NSCLC) patients receiving radical radiotherapy, which will be useful for selecting appropriate patient population for further intervention and future trial design. Methods: This was a retrospective cohort study. Patients with inoperable stage IIB-IIIC NSCLC were treated consecutively with definitive thoracic radiotherapy from January 2018 to December 2021, and were retrospectively reviewed and enrolled. Patients with various clinical variables were analyzed to clarify their impact on BM with competing risk models by Fine and Gray. Results: A total of 134 patients were enrolled in this study. The median follow-up for all patients was 37 months [95% confidence interval (CI): 30.5-43.5 months]. BM occurred in 25 patients at the time of analysis. The 1-year and 3-year cumulative BM incidence were 10.5% and 19.9%, respectively. Patients with BM had worse overall survival than those without BM [stratified hazard ratio (HR) for death: 2.83; 95% CI:1.31-6.11; P<0.001]. Based on univariate analyses, non-squamous cell carcinoma (non-SCC), biological effective dose (BED) and planning target volume (PTV) were used as input variables in multivariable analysis (P<0.01). According to multivariate analysis, non-SCC (P<0.001; HR: 6.08; 95% CI: 2.26-16.37), BED <72 Gy (P=0.017; HR: 2.81; 95% CI: 1.20-6.57), and PTV >157.73 cm(3) (P=0.043; HR: 2.56; 95% CI: 1.03-6.35) were independent risk factors for BM. In subgroup analysis of adenocarcinoma with known epidermal growth factor receptor (EGFR) mutation status, PTV >157.73 cm(3) and positive EGFR mutation were independent predictors for BM. Conclusions: In this retrospective study, we found that BED <72 Gy and PTV >157.73 cm(3) were significantly associated with BM development and we validated that non-SCC and positive EGFR mutation were risk factors for BM. More research is required to screen the high-risk patient population.