International Journal of Clinical Case Reports 2024, Vol.14, No.3, 167-177 http://medscipublisher.com/index.php/ijccr 168 still limited by factors such as poor immunogenicity and the immunosuppressive tumor microenvironment (Monnot and Romero, 2018); Basu et al., 2019). This study is to provide a comprehensive analysis of the current state of breast cancer immunotherapy, focusing on its efficacy, challenges, and future directions. By examining case-based studies and clinical trials, we seek to elucidate the factors that influence the success of immunotherapy in breast cancer and identify potential strategies to overcome existing barriers. The scope of this study includes an evaluation of various immunotherapeutic modalities, their clinical outcomes, and the ongoing research efforts aimed at enhancing the therapeutic efficacy of immunotherapy in breast cancer. 2 Overview of Breast Cancer Immunotherapy 2.1 Types of immunotherapy 2.1.1 Immune checkpoint inhibitors Immune checkpoint inhibitors (ICIs) are a class of drugs that block proteins used by cancer cells to evade the immune system. The most notable ICIs target CTLA-4, PD-1, and PD-L1 pathways. These inhibitors have shown remarkable success in treating various cancers, including breast cancer, by enhancing the immune response against tumor cells (Esteva et al., 2019; Macri and Mintern, 2019). Bagchi et al. (2020) has shown that the high frequencies of memory CD4+ and CD8+ T cells before and after ICI treatment is associated with a good response to treatment. However, the mechanism by which these T cells promote favorable therapeutic outcomes is still unclear. In addition, different TCR libraries are also associated with effective treatment (Figure 1). However, the efficacy of ICIs in breast cancer has been limited, necessitating combination strategies to improve outcomes (Darvin et al., 2018). Figure 1 The immune cell types and their correlation to ICI therapy outcome (Adopted from Bagchi et al., 2020) Image caption: ICI, immune checkpoint inhibitor; MDSC, myeloid-derived suppressor cell; NSCLC, non-small-cell lung cancer; TCR, T cell receptor; Treg, regulatory T cell (Adopted from Bagchi et al., 2020). 2.1.2 CAR-T cell therapy Chimeric Antigen Receptor (CAR) T-cell therapy involves genetically modifying a patient's T cells to express receptors specific to cancer antigens. This approach has shown dramatic results in hematological malignancies and is being explored for solid tumors, including breast cancer (Khalil et al., 2016; Lohmueller and Finn, 2017).
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