Efficacy of trastuzumab in unselected patients with HER2-positive metastatic breast cancer: a retrospective analysis.

Aims and background. The addition of trastuzumab to chemotherapy for HER2-positive metastatic breast cancer has significantly improved progreision-free survival and overall survival, although most patients develop resistance or have a primarily resistant disease. The aim of the study was to describe the efficacy and safety of a firstline treatment in unselected metastatic HER2-positive breast cancer patients, treated according to clinical practice. Methods. From 2000 to 2009, we conducted a retrospective multi-institutional analysis of 182 consecutive patients with HER2-positive metastatic breast cancer who underwent first-line treatment with trastuzumab. The primary end points were progression-free survival and overall survival; the secondary end points were survival after progression in patients treated with second-line chemotherapy with or without trastuzumab and safety. A total of 172 patients were analyzed. Results. Median progression-free survival and overall survival were 1.2 (95% CI, 1.1-1.4) and 4.4 years (95% CI, 3.6-5.4), respectively. For 100 patients who received second-line chemotherapy, median survival after progression was significantly longer in those who also received trastuzumab: 2.8 (95% CI, 2.1-4.0) versus 1.2 years (95% CI, 0.6-1.9). Conclusions. Although based on retrospective data, the study confirms the role of trastuzumab as first-line treatment in metastatic breast cancer outside of a controlled trial. Moreover, information obtained on the use of trastuzumab beyond disease progression supports its use in this setting.