Update on the Treatment of Early-Stage Triple-Negative Breast Cancer.

OPINION STATEMENT: Triple-negative breast cancer (TNBC) accounts for 15% of all breast cancers and is associated with poor long-term outcomes compared to other breast cancer subtypes. Currently, chemotherapy remains the main modality of treatment for early-stage TNBC, as there is no approved targeted therapy for this subtype. The biologic heterogeneity of TNBC has hindered the development and evaluation of novel agents, but recent advancements in subclassifying TNBC have paved the way for further investigation of more effective systemic therapies, including cytotoxic and targeted agents. TNBC is enriched for germline BRCA mutation and for somatic deficiencies in homologous recombination DNA repair, the so-called "BRCAness" phenotype. Together, germline BRCA mutations and BRCAness are promising biomarkers of susceptibility to DNA-damaging therapy. Various investigational approaches are consequently being investigated in early-stage TNBC, including immune checkpoint inhibitors, platinum compounds, PI3K pathway inhibitors, and androgen receptor inhibitors. Due to the biological diversity found within TNBC, patient selection based on molecular biomarkers could aid the design of early-phase clinical trials, ultimately accelerating the clinical application of effective new agents. TNBC is an aggressive breast cancer subtype, for which multiple targeted approaches will likely be required for patient outcomes to be substantially improved.