Expression of truncated HER2 and its prognostic value in HER2-positive breast cancer patients

The purpose of this work was to assess the truncated form of human epidermal growth factor receptor 2 (HER2) such as p95-HER2 expression in HER2-positive breast cancer (BC) patients who developed metastatic disease after adjuvant treatment with a trastuzumab-containing regimen. Thirty-two histologically diagnosed HER2-positive BC patients who developed distant failure after treatment with trastuzumab-based chemotherapy (CT) regimen as an adjuvant therapy were included in the study. Immunohistochemistry (IHC) method was used to analyze p95-HER2 expression in the formalin-fixed, paraffin-embedded (FFPE) blocks of the enrolled patients. p95-HER2 was positive in 34.4% of the patients. The median overall survival (OS) was 22.5 and 35 months for p95-HER2 positive and negative patients, respectively (p = 0.036) and the median time to metastases was 14 and 21 months, respectively (p = 0.006). There was a statistically significant association between positive p95-HER2 expression and negative hormonal receptors expression (p = 0.004), high Ki-67 expression (p < 0.001) and development of visceral metastasis (p = 0.034). Expression of p95-HER2 in HER2-positive BC patients is significantly associated with negative hormonal receptors expression, high Ki-67 expression, presence of visceral metastases and worse overall survival. A larger study is required to confirm its association with different prognostic factors and its effect on survival.