Development of new predictive markers for endocrine therapy and resistance in breast cancer.

Today, the decision to treat breast cancer patients with endocrine therapy relies solely on tumor expression of two predictive factors, the estrogen receptor and the progesterone receptor. Expression of these hormone receptors are, however, not a guarantee for a response to treatment and patients who experience response at first may become resistant after prolonged treatment. This paper describes the use of preclinical models to identify mechanisms and new markers for endocrine sensitivity and resistance and the translation of these data to clinical utility.