Narrative review on advancing breast cancer treatment: harnessing the power of PD-1/PD-L1 inhibitors for improved patient outcomes.

Background and Objective: Cancer immunotherapy has significantly advanced the field of oncology, providing novel therapeutic strategies for various malignancies, including breast cancer. The programmed cell death protein 1/programmed cell death-ligand 1 (PD-1/PD-L1) pathway is pivotal in immune regulation, and its inhibitors have demonstrated therapeutic benefits in diverse tumors. This review aims to critically examine the role, clinical efficacy, safety, and future directions of PD-1/PD-L1 inhibitors in breast cancer treatment, with a focus on pembrolizumab, nivolumab, and tislelizumab, and to elucidate the challenges and prospects in this dynamic field. Methods: A comprehensive literature search was conducted, adhering to Narrative Review reporting checklist for transparent reporting. Data from selected studies were qualitatively analyzed to synthesize key findings related to the mechanisms of action, clinical applications, and challenges of PD-1/PD-L1 inhibitors in breast cancer. Key Content and Findings: PD-1 inhibitors have shown remarkable efficacy in various malignancies, including advanced triple-negative breast cancer (TNBC), where they have been investigated both in combination with chemotherapy and as neoadjuvant/adjuvant treatment. The exploration of these inhibitors in other breast cancer subtypes, such as human epidermal growth factor receptor-positive and hormone receptor-positive breast cancer, is ongoing. The review highlights the challenges in patient selection, management of immune-related adverse events (irAEs), and the emergence of resistance mechanisms. It underscores the need for ongoing research focusing on identifying reliable predictive biomarkers, elucidating mechanisms of resistance, and optimizing treatment strategies. Conclusions: PD-1/PD-L1 inhibitors hold substantial promise in advancing breast cancer treatment. This review provides critical insights and emphasizes the clinical importance of continued scientific exploration to refine patient selection criteria, improve treatment outcomes, and expand the applications of immunotherapy in breast cancer. Further research is imperative to overcome the existing challenges and realize the full therapeutic potential of these inhibitors in breast cancer and other malignancies.