Moderate level of HER2 expression and its prognostic significance in breast cancer with intermediate grade

Overexpression of human epidermal growth factor receptor 2 (HER2) is an important prognostic and predictive marker of response to anti-HER2 therapy in breast cancer. Our goal was to analyze the prognostic significance of moderate expression of HER2 in breast cancer with intermediate differentiation grade. We performed a multicenter retrospective register study of 8494 patients with primary non-metastatic breast cancer admitted between 2000 and 2011 to eight Clinics in Saxony-Anhalt, federal state of Germany. Patients were divided into three groups according to their HER2 score: 4073 were classified as HER2 negative (HER2 0 and 1+), 822 HER2 moderate (HER2 2+/ HER2 ), and 1238 HER2 positive (HER2 3+ or HER2 2+/ HER2 +). HER2-positive cases were excluded from analysis. Tumors with moderate HER2 (HER2 2+) expression demonstrated an aggressive behavior and worse patient survival compared with HER2 0 and 1+ status. HER2 2+ status was associated with shorter median overall survival (OS) ( P