The Evolving Landscape of Immune Checkpoint Inhibitors and Antibody Drug Conjugates in the Treatment of Early-Stage Breast Cancer

Abstract For decades, chemotherapy has been the mainstay of breast cancer treatment. Novel therapies are expanding the therapeutic options and altering the treatment algorithms to manage this disease. The use and approval of immune checkpoint inhibitors (ICIs) and antibody-drug conjugates (ADCs) represent a few areas of progress. These therapies initially gained attention in the metastatic setting but have subsequently found a role in early-stage breast cancer. Although human epidermal growth factor receptor 2 (HER2) is at the center of ADC development, other surface antigens with a differential expression between tumor and normal cells may be appropriate for ADC targeting. This has led to the discovery of new ADCs targeting other receptors, including TROP-2, HER-3, and LIV-1, to name a few. Similarly, the addition of pembrolizumab in treating early-stage triple-negative breast cancer has led to exploring other ICIs in this setting. However, it has also raised important scientific questions regarding optimal patient selection, biomarkers that predict the success of ICIs, ideal chemotherapy partners, and the financial implications of bringing newer therapies to the forefront. In this review, we discuss the evolving landscape of ICIs and ADCs in managing early-stage breast cancer and provide an overview of potential future advancement in the field.