Adjuvant application of trastuzumab in HER2 positive breast cancer and impact on time to relapse

Received 2018-11-12 Received in revised form 2019-05-22 Accepted 2019-05-29 INTRODUCTION Breast cancer is the most common malignant disease in women (1). It makes up about 26.5% of all newly discovered malignancies in the European female population and is responsible for 17.5% of the deaths. In males, this type of cancer is rare (one man per 100 women) (2). The frequency of the disease differs in various parts of the world. It is rarely seen before the age of 30, it rises with age and reaches its maximum around the age of 50 (3). The incidence of breast cancer in the world increases by 1-2% per year, and it is estimated that in the first decade of the third millennium, almost one million of women will suffer from breast cancer (4). However, in spite of the increasing possibilities of treatment, survival depends primarily on the extent and stage of the disease at the time of detection. In the early stage of the disease in which the largest number of patients is detected, healing is quite possible. Still, 24-30% of patients with lymph node negative and 50-60% with lymph node positive breast cancer will develop relapse. At the moment of diagnosis metastatic disease is present in 6-10% of patients (5). Treatment of breast cancer is multidisciplinary. Combination of surgical treatment, radiation and systemic therapeutic treatment ensure good results in patient survival. The type and order of particular treatments must be planned multidisciplinary by surgeons-oncologists, radiotherapists and internists-oncologists (6). Clinical features of tumor such as size, the existence of tumor cells in the armpit lymph nodes, and distant metastases are considered essential in determining prognosis and choices of treatment. Prognostic factors, derived from breast tissue after biopsy or surgery, have significance in measuring tumor aggressiveness and general disease prognosis. The standard prognostic parameters are patient (menopausal status, age) and tumor related (tumor size, histological type, axillary lymphatic status, tumor gradient, ER, PR and HER2 status). Some of them (ER, PR and HER2 status) have a predictive value because the best therapeutic modality is chosen based on these. According to St. Gallen Consensus and ESMO recommendations from year 2013 breast cancers fall into different types according to histopathological findings and results of predictive and prognostic tests. Based on this, specific therapeutic approach is recommended. When luminal A type patient receive only endocrine therapy, and chemotherapy is considered only in cases of high risk tumor (with four or more positive lymph nodes, tumor size T3 or tumor grade 3). When luminal B-like type (HER2 negative) patient is treated using chemotherapy and endocrine therapy. When luminal B-like (HER2 positive) patient is treated using chemotherapy, anti-HER2 and endocrine therapy. In case of non-luminal (HER2 positive) breast cancer type chemoand anti-HER2 therapy is recommended. In patients with basal-like (triple-negative) cancer application of chemotherapy is indicated (7).