Metastatic breast cancer: are we treating the same patients as in the past?

Early detection and improved (neo)-adjuvant treatment has extended survival of breast cancer over the last decades. It remains controversial whether a survival benefit is achieved once metastases have occurred. This study investigates survival trends in metastatic breast cancer (MBC) looking at the distribution of prognostic factors and the time period of the diagnosis of the primary and metastatic disease.

In this retrospective study, 1635 patients, diagnosed with MBC and treated at three German cancer centers, were included. For the survival analysis, patients were grouped into three time periods [1980-1994 (a), 1995-1999 (b) and 2000-2009 (c)], which were chosen according to the availability of new antineoplastic drugs for the treatment of MBC. Additionally, patients were divided into three risk groups using the simultaneously published prognostic score.

The analysis of overall survival according to the date of primary diagnosis demonstrated a significant decline compared with the reference (a): (a versus b) hazard ratio (HR) = 1.37; P < 0.001; (a versus c) HR = 2.45; P < 0.001. Considering the time of first occurrence of metastasis, survival remains unchanged over the three periods (a versus b): HR = 0.94 P = 0.436; (a versus c): HR = 0.95; P = 0.435. However, a significant shift towards more unfavorable risk factors was seen.

Although survival in MBC remains unchanged over time, patients developing metastatic disease have a more aggressive disease that is presumably compensated by more effective treatment. This alteration of tumor biology in MBC may be explained by a negative selection of patients with adverse risk profiles due to the advantages of the adjuvant therapy.