Predictive Biomarkers and Targeted Therapies in Breast Cancer

Abstract

Breast cancer is the most common cancer in women and accounts for more than 250, 000 cases in the USA alone. Although a poster child for predictive markers and targeted therapies, progress in treatment for this cancer has been slow. This is particularly true for new predictive biomarkers, and the number of routinely assessed predictive markers is restricted to estrogen, progesterone, and human epidermal growth factor receptors. Proliferation plays an important role in prognostication of ER+ tumors; however, its role in prediction is uncertain. Cell cycle (CDK4/CDK6) inhibitors such as palbociclib/ribociclib have been demonstrated to have a place in the management of ER+ cancers. HER2 positivity predicts for response to a number of anti-HER2 targeted therapies. Patients with BRCA1/BRCA2 mutations respond well to PARP inhibitor (PARPi; e.g., olaparib) therapy. The role of PARPi in other types of breast cancer remains to be established. The high prevalence of breast cancer and failure of standard of care therapies have resulted in intense focus on developing novel therapies including targeted therapies. A number of agents have been tried either in combination with endocrine therapy and/ or chemotherapy for the treatment of metastatic cancer.