A narrative review of biomarkers in advanced triple negative breast cancer

Triple negative breast cancer (TNBC) is a heterogeneous disease; while clinically diagnosed as a single entity disease, at the molecular level, TNBC includes characteristic subtypes with potential for subtype specific targeted therapies which are still underway. Chemotherapy remains the backbone of treatment of TNBC. Although new targeted therapies have been introduced in the metastatic setting, including immunotherapy, PARP inhibitors and antibody drug conjugates (ADC), identifying patients who would selectively benefit from these treatments is awaiting a more refined selection process driven by better understanding of the biology of TNBC subtypes. More importantly, there is a need for validated tools of genomic precision and biomarker driven targeted therapy that can readily identify TNBC subtypes in the clinic and translate complex molecular analysis into individualized treatment plans for patients. This review presents biomarkers in advanced TNBC with potential for targeted therapies and discusses ongoing strategies to managing the heterogeneity of TNBCs. We discuss biomarkers including TP53, androgen receptor, breast cancer susceptibility genes (BRCA), homologous recombination deficiency (HRD), PI3K/AKT/mTOR, immune biomarkers, and ADC. The review concludes with a summary of the landscape of biomarker driven targeted therapies in advanced TNBC that has been improving outcomes of this aggressive disease.