Estrogen receptors: Role in breast cancer

square The estrogen receptor (ER) exists in two forms known as ER alpha and ER beta. Currently, a clinical role has only been established for ER alpha. The primary use of ER alpha in breast cancer is for predicting likely response to hormone treatment. Patients with breast cancers expressing ER alpha are approximately seven to eight times more likely to benefit from endocrine therapy than ER alpha-negative patients. For the initial three to five years after primary diagnosis, ER alpha-positive patients generally have a better outcome than ER alpha-negative patients. Overall, however, the prognostic value of ER alpha is relatively weak and only of limited value in the clinically important subgroup of patients with lymph node-negative disease. Further work is required to establish if ER beta has a clinical role in breast cancer.