The androgen receptor in breast cancer: learning from the past

Excerpt

Care of the cancer patient is becoming increasingly individualized. At the fulcrum of such therapeutic decision-making lies a relevant and accurate understanding of unique patient characteristics and preferences, and of tumor biology. In a pure sense, prognostic factors reflect tumor biology that may be used to estimate outcome independent of systemic treatment, whereas predictive factors reflect a relative resistance or sensitivity to specific therapy(ies) and are increasingly used to select optimal treatments for an individual patient. Perhaps the best and oldest example of a biomarker with proven clinical utility is the estrogen receptor alpha (ER), the expression of which on breast tumors has served both as a prognostic and predictive biomarker for the last three decades [1]. The Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) 2005 overview clearly demonstrated that tamoxifen substantially reduces the risk for breast cancer recurrence and death across all age groups in patients with ER-positive early-stage breast cancer, whereas patients with ER-negative disease do not benefit from tamoxifen [2, 3]. ER status also predicts response to endocrine therapy in the metastatic setting [4]. In this issue of Breast Cancer Research and Treatment, a well designed and thorough study by Castellano et al. [5] explores the concept of androgen receptor (AR) as a novel prognostic factor in ER-positive breast cancer, and suggests that it may have additional clinical utility in identifying a better prognosis subgroup of luminal B breast cancers. …