Trastuzumab in Human Epidermal growth Receptor 2-positive (HER2+) metastatic breast cancer (MBC) was established as standard therapy since 2001. The objective of this study was to search for significant prognostic factors in patients with HER2+ MBC treated by trastuzumab taking into account the institution where the treatment was given.

All patients with HER2+ MBC treated by trastuzumab between 2001 and 2010 in the 8 hospitals of Franche Comte region were analysed. Univariate and multivariate analysis were conducted to search for factors related to overall survival (OS).

Among 1234 patients with MBC treated by chemotherapy between 2001 and 2010, 217 patients received trastuzumab. In this subset, the median age was 60 years, 8% and 38% had brain and liver metastases at first occurrence of MBC, 36% of, tumours were hormonal receptors positive. Patients were treated in 48% and 52% of cases in specialized and in general hospitals, respectively. The median OS length was 45.2 months (IQR 23.2-89.3 months). In univariate analysis the following factors were significantly related to favourable OS: inclusion in clinical trials, treatment in a specialized hospital, positive hormonal receptors status, age <50. In multivariate analysis remained significant: treatment in specialized hospital (aHR 0.78; 95%CI 0.64-0.94; p = 0.03) and age <50 (aHR 0.76; 95%CI 0.59-0.95; p = 0.02).

Exposure to trastuzumab erases all established prognostic factors at the metastatic setting. The fact that patients treated in specialized hospitals presented a longer survival emphasizes the dramatic impact of this therapy and the relevance to optimize its use.