Genomic Signatures in Luminal Breast Cancer

Background:Breast cancer is a very heterogeneous disease and luminal breast carcinomas represent the hormone receptor-positive tumors among all breast cancer subtypes. In this context, multigene signatures were developed to gain further prognostic and predictive information beyond clinical parameters and traditional immunohistochemical markers.Summary:For early breast cancer patients these molecular tools can guide clinicians to decide on the extension of endocrine therapy to avoid over- and undertreatment by adjuvant chemotherapy. Beside the predictive and prognostic value, a few genomic tests are also able to provide intrinsic subtype classification. In this review, we compare the most frequently used and commercially available molecular tests (OncotypeDX (R), MammaPrint (R), Prosigna (R), EndoPredict (R), and Breast Cancer Index(SM)). Moreover, we discuss the clinical utility of molecular profiling for advanced breast cancer of the luminal subtype.Key Messages:Multigene assays can help to de-escalate systemic therapy in early-stage breast cancer. Only the Oncotype DX (R) and MammaPrint (R)degrees test are validated by entirely prospective and randomized phase 3 trials. More clinical evidence is needed to support the use of genomic tests in node-positive disease. Recent developments in high-throughput sequencing technology will provide further insights to understand the heterogeneity of luminal breast cancers in early-stage and metastatic disease.