Human epidermal growth factor receptor 2 status in breast cancer: A comparison between borderline positive human epidermal growth factor receptor 2 and strongly positive human epidermal growth factor receptor 2 tumors

Background: Human epidermal growth factor receptor 2 (HER2) status is an important biomarker and a molecular target for specific therapies such as humanized monoclonal antibody - trastuzumab. The aim of this study was to compare a group of the borderline positive HER2 (++) status patients with a strongly positive HER2 (+++) status group, according to clinicopathological features, cardiotoxicity, and treatment response. Materials and Methods: The analysis included medical records of 166 early and metastatic breast cancer patients treated with trastuzumab. Results: There were no significant differences between both groups in relation to patients′ age at initial diagnosis and comorbid conditions; however, diabetes (4%) were observed only in tumors with strong HER2 overexpression. Patients with HER2 (+++) more frequently had a history of cigarette smoking in comparison with HER2 borderline women (39% vs. 25%, P = 0.06). There was no association between overweight and HER2 status. No statistically significant differences in steroid receptor status were detected between HER (++) and HER2 (+++) positive tumors (P = 1.00). Borderline tumors were in earlier stage of disease (50% vs. 17%, P = 0.002). Lymph node metastases correlate with strongly positive breast cancer (58% vs. 33%, P = 0.04). Second neoplasm also more often developed in strongly positive HER2 tumors and contralateral breast cancer in borderline. Conclusion: In the summary, borderline positive HER2 breast cancer patients are in earlier advance stage and have a better outcome than strong positive HER2 tumors. They are less predisposed to the development of cardiac side effects. Type 2 diabetes coexisted with strong HER2 overexpression.