Immunotherapies against HER2-Positive Breast Cancer

SIMPLE SUMMARY: A wide range of treatments are available for HER2-positive breast cancer, which have greatly improved the prognosis and quality of life of these patients. However, resistance to HER2-targeted or untargeted therapies is common in clinical practice and is associated with metastasis, recurrence, and cancer-related death. To address this clinical need, researchers are exploring immunotherapeutic approaches to completely eradicate tumor cells and prevent tumor relapse and progression. In this review, we focus on how these emerging strategies can overcome current resistance and improve the prognosis of patients who do not respond to standard therapies. ABSTRACT: Breast cancer is the leading cause of cancer-related deaths among women worldwide. HER2-positive breast cancer, which represents 15–20% of all cases, is characterized by the overexpression of the HER2 receptor. Despite the variety of treatments available for HER2-positive breast cancer, both targeted and untargeted, many patients do not respond to therapy and relapse and eventually metastasize, with a poor prognosis. Immunotherapeutic approaches aim to enhance the antitumor immune response to prevent tumor relapse and metastasis. Several immunotherapies have been approved for solid tumors, but their utility for HER2-positive breast cancer has yet to be confirmed. In this review, we examine the different immunotherapeutic strategies being tested in HER2-positive breast cancer, from long-studied cancer vaccines to immune checkpoint blockade, which targets immune checkpoints in both T cells and tumor cells, as well as the promising adoptive cell therapy in various forms. We discuss how some of these new approaches may contribute to the prevention of tumor progression and be used after standard-of-care therapies for resistant HER2-positive breast tumors, highlighting the benefits and drawbacks of each. We conclude that immunotherapy holds great promise for the treatment of HER2-positive tumors, with the potential to completely eradicate tumor cells and prevent the progression of the disease.