Prognostic Significance of Human Epidermal Receptor (HER)-3 Immunohistochemical Expression in Patients with Metastatic Breast Cancer

Background: Previous reports have shown that human epidermal receptor (HER)-3 overexpression may beassociated with poor prognosis in patients with breast cancer, but results have been conflicting. In this study,we sought to investigate the prognostic significance of HER-3 immunohistochemical expression in patients withmetastatic breast cancer.
Methods: We retrospectively analyzed HER-3 immunohistochemical expression profilesin 45 paraffin-embedded specimens from patients who had been treated between 1996 and 2006 in the Departmentof Oncology of the Uludag University School of Medicine, Bursa, Turkey. Membranous or cytoplasmic dominantexpression patterns of HER-3 were analyzed using the Rajkumar score and a cytoplasmic 4-point scoring system,respectively. Progression-free survival (PFS) and overall survival (OS) served as the main outcome measures.
Results: The median PFS in the study participants was 9 months (interquartile range: 4.5-13 months), whereasthe median OS was 20 months (interquartile range: 7.5-28 months). Categorization of the patient populationaccording to HER-3 positive immunohistochemical expression did not reveal any statistically significant differencein terms of both PFS (p=0.70) and OS (p=0.81). The results of multivariable Cox regression analysis indicatedthat tumor size was the only independent predictor of PFS, whereas estrogen and progesterone receptor statuswas independently associated with OS.
Conclusions: HER-3 immunohistochemical expression did not correlatewith outcomes in Turkish patients with metastatic breast cancer. Although our results suggest that HER-3expression in cancer specimens is not of prognostic significance, further prospective studies are warranted toconfirm these results.