Triple negative breast cancer (TNBC) is the subgroup of tumours that do not express clinically significant levels of the estrogen receptor (ER), progesterone receptor (PgR) and the human epidermal growth factor 2 receptor (HER2). Approximately 10-24% of invasive breast cancers diagnosed are TNBC, depending on demographics of the patient population. With the possible exception of BRCA-null cases and their sensitivity to PARP inhibition, patients with TNBC have no established options for systemic therapy other than chemotherapy. TNBCs tend to initially respond to chemotherapy, but have a higher frequency of early relapse with visceral and CNS metastases and poor overall survival. This highlights a critical need to identify effective systemic targeted therapies for this disease.

This presentation will focus on recent advances to characterize and target the molecular pathology operating in biologic sub-contexts of TNBC. This will include data from two recent studies identifying 1) the Folate Receptor-alpha (FOLR1) and 2) the Androgen Receptor (AR) as attractive, novel, molecularly informed therapeutic strategies for these patients. With respect to AR expression, we observe AR positivity in 23 % of TNBC cases with 10-43% AR positivity observed by others. We further observe AR-positive TNBCs to have distinct clinical features, including a higher propensity for lymph node involvement and poorer recurrence-free survival. These studies highlight important new opportunities emerging for evidence-based treatment strategies for patients with TNBC, who to this point have no options for targeted therapy.