Current value and future potential of biological markers in breast cancer

Over the last 25 years, many studies have confirmed that oestrogen receptor (ER) content is a good indicator of response to endocrine therapy in breast cancer. However, there is little information that allows such clear selection of therapy for patients with ER negative disease (ER(-)). There are at least 8 classes of biomarkers that can be described. Studies are urgently needed to determine which combinations of these classes of markers will give the best tools for optimal management of breast cancer patients.