A new instrument for predicting survival of patients with cerebral metastases from breast cancer developed in a homogeneously treated cohort
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 (p<0.05) associations with OS on univariate analysis or almost significant (p<0.055) associations 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 diagnosis-specific 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 univariate analyses, better OS was significantly associated with KPS >70% (p<0.001) and absence of extra-cerebral metastases (p=0.001). On multivariate analysis, KPS was significant (p<0.001); time between breast cancer diagnosis and WBRT was almost significant (p=0.053). 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.