Horizons of personalized medicine in breast cancer treatment: review article

Breast cancer that is caused by the accumulation of genetic and epigenetic alterations, is one of the main causes of death resulted from cancer. Various therapeutic approaches have been introduced for this cancer and the traditional diagnosis and treatment is based on the prognosis estimation using cancer anatomic features (TNM system) and clinical results, but studies show different responses of these treatments and recurrence after those in some patients. This diversity is resulted by the differences in biological and molecular characteristics. So genomic and molecular studies became more important and the role of targeted treatment based on an individual's genome was highlighted. Today, the progression in personalized medicine using specific individual genome profile has been possible. The ultimate goal of such studies, in the setting of the personalized medicine, is providing markers which can be used to risk assessment of progressing disease. This new science cause great development in the treatment of breast cancer by recognition of specific markers and application of targeted therapy. Trastuzumab and tamoxifen are the most common monoclonal antibodies applied in these patients depends on their biological and molecular profile. The good response to tamoxifen is seen only in patients with estrogen receptor (ER) which inhibits the binding of estrogen to its receptor. Defect in the metabolizer enzyme of tamoxifen (CYP2D6), which convert it to the active forms, results in the increased risk of recurrence after treatment. Fulvestrant is another monoclonal antibody which its effect is similar to tamoxifen. Trastuzumab suppresses the cell growth by binding inhibition of epidermal growth factor to HER2 receptors. In the metastatic form of disease, the patients may show resistance to trastuzumab, so lapatinib is suitable alternative in these cases. Pertuzumab combination with trastuzumab and chemotherapy with taxane blocks the dimerization of HER2 with another form of HER receptors. The application of personalized medicine in triple negative phenotype is limited due to the lack of appropriate targets and biomarkers, it makes necessary to do further studies. The aim of this review was to describing the different aspects of personalized medicine and introducing the most important biomarkers and targets in the treatment of breast cancer.