Resistance to Immunotherapy in Breast Cancer

Breast cancer is the most common and second most deadly disease in women worldwide, with breast cancer screening resulting in a steady decline in mortality rate. However, early diagnosis of breast cancer for young black women has not improved the mortality rate due to aggressiveness, and the ability to grow faster resulting in potential metastasis and recurrence, especially in the triple-negative molecular subtype. This prompted the decision to first investigate the efficacy of immunotherapy, particularly immune checkpoint inhibitors (ICIs). However, ICIs are only successful in a small group of patients expressing programmed cell death ligand (PD-L1) and most patients develop toxicity and drug resistance. High levels of tumor-infiltrating T cells have been shown to be a favorable indicator of therapeutic response indicating that immunotherapy can be utilized to harness the power of the immune system to recognize and destroy cancer cells. This chapter will focus on the utilization of immunotherapy as a potential solution to overcome drug resistance in breast cancer. The chapter will explore various immunotherapeutic approaches, including ICIs, adoptive cell transfer, and bispecific antibody therapies. These therapies aim to enhance the immune response against cancer cells and overcome mechanisms of drug resistance. By leveraging the body’s natural defenses, immunotherapy holds promise in revolutionizing breast cancer treatment and improving patient outcomes.