CTLA4 and breast cancer: Immune checkpoint inhibitors (ICIs), such as programmed cell death (PD-1), programmed cell death ligand-1 (PD-L1), and cytotoxic T-lymphocyte associated antigen-4 (CTLA-4), in combination with chemotherapeutic regimens have higher efficacy than ICI monotherapy in treating patients with IM subtype BC [44,45].