Comparison of Breast Graded Prognostic Assessment Scores in a Turkish Cohort of Patients with Brain Metastatic Breast Cancer

Breast Graded Prognostic Assessment (B-GPA), modified B-GPA (mB-GPA), and updated B-GPA (uB-GPA) are the best-known prognostic tools used to stratify survival in patients with brain metastatic breast cancer. However, clinically important variables, such as extracranial disease (ECD) status, was not included in these models. We aimed to evaluate the utility of these three prognostic tools in a Turkish cohort and investigate the prognostic value of ECD status. Data from breast cancer (BC) patients diagnosed with brain metastasis (BM) between January 2012 and December 2022 were collected retrospectively. Patients were classified according to B-GPA, mB-GPA, and uB-GPA scores. Univariate and multivariate analyses were performed using the Cox proportional hazards model to investigate prognostic factors for overall survival (OS). The Kaplan-Meier method was used to estimate OS, and the log-rank test was used to compare survival between scores. B-GPA, mB-GPA, and uB-GPA performances were compared using Harrell’s concordance index. In our cohort of 199 patients, B-GPA, mB-GPA, and uB-GPA were confirmed to be useful prognostic tools for OS and showed excellent discrimination between survival curves (p< 0.001). We found that the uB-GPA’s C-index of 0.689 significantly better predicted OS than the other two tools. ECD status was shown to be an important predictor of OS in univariate and multivariate analyses (p< 0.001). Including ECD status as a factor in the uB-GPA test increased the C-index to 0.709 (log-rank p< 0.0001). ECD status provides independent prognostic information beyond the prognostic scores commonly used in BCBM. Keywords: Breast cancer, Brain metastasis, Survival outcomes, Prognostic index, Updated B-GPA