B2- prognostic score: External validation of a clinical decision-making tool for metastatic breast cancer

Abstract Background The B 2 Prognostic Score (B 2 PS) is a clinical decision-making tool in metastatic breast cancer (MBC) that provides risk classification based on routine parameters. This study validates the B 2 PS in an independent series of MBC for the whole study group and for each intrinsic subtype. Methods We analyzed 641 metastasized patients, treated in 17 German certified breast cancer centers between 2001 and 2009. They were classified into low, intermediate and high-risk groups according to B 2 PS. Overall survival (OS) curves for the various B 2 PS-groups were compared with Kaplan-Meier method with log-rank test respectively with Cox regression. Results According to the B 2 PS-formula, 42.3 % of patients were classified as low-risk, 25.4 % as intermediate-risk and 32.3 % as high-risk. Intermediate and high-risk patients had a statistically significant decreased OS compared to B 2 PS-low-risk patients: (intermediate-risk: hazard ratio (HR) 1.36, 95 % confidence interval (CI) 1.04-1.77, p=0.023; high-risk: HR 2.62, 95 % CI 2.06-3.32, p 2 -risk groups varied significantly within the intrinsic subtypes. For each intrinsic subtype B 2 PS gives an additional risk classification. Conclusions This study demonstrates the reproducibility of the B 2 -score based on routinely assessable parameters and confirmed its prognostic value in an independent entire cohort of MBC as well as in the seperate intrinsic subtypes. It therefore can help in counseling and individualizing therapeutic regimens of those patients.