Breast cancer is a heterogeneous disease. The purpose of adjuvant therapy for early-stage breast cancer is to provide maximum benefit with minimum side effects and not to under-treat or over-treat. The clinical progresses of patients with the same clinical and pathological characteristics who are given similar treatments may show major differences. This fact indicates that the prognostic and predictive factors that we have used until recent years for therapy selection are not really sufficient, we need new markers, every disease and every individual are unique and that treatment should be individualized. The gene expression profiling, which has come into clinical use in recent years, is beneficial in therapy selection for luminal breast cancer cases. A differentiation can be made among patients for whom only endocrine treatment would be adequate and those who should also receive chemotherapy in addition to endocrine treatment. Several new gene expression analysis studies targeted at gaining the ability to determine drug selection in chemotherapy, endocrine treatment and neo-adjuvant therapy are also currently ongoing. The staging system for new breast cancer that is to be published in the year 2018 also includes gene expression analyses within the prognostic panel and the stage changes depending on the result. The statement 'Treat the patient, not the disease.' is becoming increasingly entrenched in our clinical practice. This article briefly summarizes the gene expression profiles, which are validated and used in the selection of therapy for early-stage breast cancer.
Keywords: Early breast cancer; gene-expression profiling; molecular subtypes; prognosis; staging.