HER2/neu role in breast cancer: from a prognostic foe to a predictive friend

Purpose of review The principal effort of this review was to elucidate the role of human epidermal growth factor receptor 2/neu expression in breast cancer, either as an independent prognostic factor or a predictive marker of response to antineoplastic therapy, in light of the most recent results obtained with the use of trastuzumab, in either the metastatic or the adjuvant setting. Recent findings Human epidermal growth factor receptor 2-overexpressing breast cancer is known to be associated with particularly aggressive disease and poor prognosis. On the other hand, human epidermal growth factor receptor 2/neu overexpression may predict response to endocrine therapy or chemotherapy. Nevertheless, trastuzumab increases the clinical benefit of first-line chemotherapy in patients with metastatic breast cancers that overexpress human epidermal growth factor receptor 2. Decades of randomized clinical trials on the front-line treatment of metastatic breast cancer have never been able to show so remarkable differences in survival as recent randomized trials comparing chemotherapy with chemotherapy plus trastuzumab in women with human epidermal growth factor receptor 2-overexpressing metastatic breast cancer have been able to do. Summary In the pretrastuzumab era, retrospective analyses have shown that human epidermal growth factor receptor 2 overexpression is an adverse prognostic factor associated with an increased risk of disease recurrence and death. In the trastuzumab era, this drug has changed the natural history of human epidermal growth factor receptor 2-positive breast cancer, either in the metastatic or, according to the most recent evidences, in the adjuvant setting.