B² Prognostic Score: External Validation of a Clinical Decision-making Tool for Metastatic Breast Cancer

The B² Prognostic Score (B²PS) is a clinical decision-making tool in metastatic breast cancer (MBC) that provides risk classification based on routine parameters. This study validates the B²PS in an independent series of MBC for the whole study group and for each intrinsic subtype.

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 B²PS. Overall survival (OS) curves for the various B²PS groups were compared with Kaplan-Meier method.

According to the B²PS 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 with B²PS low-risk patients: (intermediate-risk: hazard ratio, 1.36; 95% confidence interval, 1.04-1.77; P = .023; high-risk: hazard ratio, 2.62; 95% confidence interval, 2.06-3.32; P < .001). The 5-year survival rates of low-, intermediate-, and high-risk patients were 41.3%, 26.9%, and 10.2%, respectively. The distribution of B²PS risk groups varied significantly within the intrinsic subtypes. For each intrinsic subtype, B²PS gives an additional risk classification.

This study demonstrates the reproducibility of the B²PS based on routinely assessable parameters and confirms its prognostic value in an independent entire cohort of MBC as well as in the separate intrinsic subtypes. It therefore can help in counseling and individualizing the therapeutic regimens of those patients.