Background. Previous survival scores for breast cancer patients with cerebral metastases were developed in cohorts receiving heterogeneous treatments, which could have introduced selection biases. A new instrument (WBRT-30-BC) was created from 170 patients receiving whole-brain radiotherapy (WBRT) alone with 30 Gy in 10 fractions. Methods. Characteristics showing significant associations (p lt; 0.05) with overall survival (OS) or a trend (p lt; 0.08) on multivariate analysis were used for the WBRT-30-BC. For each characteristic, 6-month OS rates were divided by 10. These scoring points were added for each patient (patient scores). The WBRT-30-BC was compared to the diagnosisspecific graded prognostic assessment (DS-GPA) classification and Rades-Score for breast cancer regarding positive predictive values (PPVs) to identify patients dying within 6 months and patients surviving at least 6 months following WBRT. Results. On multivariate analysis, Karnofsky performance score (KPS) was significant (risk ratio [RR]: 2.45, p < 0.001). In addition, extra-cerebral metastatic disease (RR: 1.52, p = 0.071) and time between breast cancer diagnosis and WBRT (RR: 1.37, p = 0.070) showed a trend. Based on these three characteristics, four predictive groups were designed: 7.9, 10.12, 13.15 and 16 points. Six-month OS rates were 8%, 41%, 68% and 100% (p < 0.001). PPVs to identify patients dying within 6 months were 92% (WBRT-30-BC), 84% (DS-GPA) and 92% (Rades-Score). PPVs to identify patients surviving for at least 6 months were 100% (WBRT-30-BC), 74% (DS-GPA) and 68% (Rades-Score). Conclusions. The WBRT-30-BC appeared very accurate in predicting death . 6 months and survival ≥ 6 months of breast cancer patients receiving WBRT. It was superior to previous instruments in predicting survival ≥ 6 months.