Emerging Targeted Therapies for Early Breast Cancer

Breast cancer is the most common malignancy and the second leading cause of cancer-related mortality in the United States (US). Most patients are diagnosed with early-stage disease; however, there is still a need to prevent recurrences that often present as incurable metastatic disease. The treatment landscape of early-stage breast cancer is evolving rapidly. The immune checkpoint inhibitor pembrolizumab is approved in combination with neoadjuvant chemotherapy for the treatment of high-risk triple-negative breast cancer (TNBC). The cyclin-dependent kinase (CDK) 4 and 6 inhibitor abemaciclib is approved for adjuvant treatment of patients with high-risk hormone receptor (HR)-positive disease. While adjuvant olaparib has shown significant improvement in outcomes for patients with pathogenic/likely pathogenic BRCA1/2 mutations and high-risk human epidermal growth factor receptor 2 (HER2)-negative breast cancer, and is approved in this setting. For the HER2-positive subtype, the post-neoadjuvant therapy can be tailored based on the response to neoadjuvant chemotherapy and HER2-targeted agents. In this narrative review, we summarize the most recent approvals for early-stage breast cancer as well as frequently encountered clinical challenges utilizing these medications.