Abstract PD13-03: Clinical and pathological variables associated with brain metastases (BrM) development among patients receiving neoadjuvant chemotherapy (NAC) for breast cancer (BC)

Abstract Background: Risk factors and timing of BrM development among patients receiving NAC for BC are not well defined. Methods: A retrospective study of two cohorts of patients at the Sunnybrook Odette Cancer Centre was conducted. Cohort 1 included 469 patients treated with NAC for BC from 2008 - 2019. Cohort 2 included 801 patients treated for BC BrM with radiation and/or surgery from 1995 - 2023, among whom 117 received NAC. After unduplicating records, 586 patients were included in the final analysis. Descriptive statistics were used to summarize patient and treatment characteristics. Cox proportional hazards regression was used to estimate hazard ratios (HR) and identify predictors of BrM. Univariable analyses (UVA) were performed for all covariates. Bayesian Information Criteria determined best models from subsets of covariates for multivariable analyses (MVA). The proportional-hazards assumption was appraised by visually inspecting graphs of Schoenfeld residuals and testing their independence over time. Statistical significance was defined as p