Breast cancer remains the most commonly diagnosed malignancy among women worldwide and continues to pose significant therapeutic challenges, particularly in advanced and refractory disease. Although traditionally considered less immunogenic compared with other solid tumours, growing evidence demonstrates that subsets of breast cancer, particularly triple-negative and HER2-positive subtypes, exhibit immune-responsive features. This recognition has spurred the development and clinical evaluation of immunotherapeutic strategies, with immune checkpoint inhibitors (ICIs) emerging as the most prominent approach. This new class of drugs targeting the programmed death-1 (PD-1)/programmed death-ligand 1 (PD-L1) axis has demonstrated meaningful clinical activity in select patient populations, leading to regulatory approvals in combination with chemotherapy for advanced triple-negative breast cancer. Despite these advances, response rates remain modest, and the benefits are largely restricted to patients with PD-L1-positive tumours. Ongoing studies are evaluating predictive biomarkers, optimal treatment combinations, and mechanisms of resistance to expand the efficacy of ICIs across broader breast cancer subtypes. Furthermore, novel checkpoint targets such as cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), lymphocyte-activation gene 3 (LAG-3), and T cell immunoreceptor with immunoglobulin and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) are under investigation, with the potential to enhance or complement PD-1/PD-L1 blockade. This review summarises the current state of knowledge on breast cancer immunotherapy with an emphasis on ICIs, highlighting key clinical trial findings, as well as emerging biomarkers of response, and strategies to overcome therapeutic resistance, if cancer cells eventually develop resistance. By integrating preclinical insights with clinical progress, we aim to provide a comprehensive overview of the evolving role of checkpoint blockade in breast cancer and outline future directions to optimise patient outcomes.

Background: The alarming trend of rising depression and insomnia among the world’s population, especially in young adults, demands urgent attention from both clinical and lifestyle medicine perspectives. This study aimed to evaluate whether habitual physical activity (PA) could improve sleep quality and depressive symptoms. It explores whether sleep parameters mediate the relationship between training intensity and depression. Methods: This cross-sectional study examined the relationships between PA, sleep quality, and depression in 349 participants, predominantly young adults, aged 16–54 (Median: 21, Q1–Q3: 20–23). Depressive symptoms and sleep quality were assessed using the Beck Depression Inventory (BDI) and Pittsburgh Sleep Quality Index (PSQI). PA parameters, including training intensity and frequency, were evaluated via a study-specific self-report tool. Mediation effects were assessed utilising Structural Equation Modelling (SEM) to evaluate direct, indirect, and total effects. Results: Higher training intensity and training volume were associated with lower depressive symptoms. Except for the daytime dysfunction domain, the current data did not support sleep as a mediator in the relationship between physical activity and depressive symptoms. Participants with 3–5 years of training experience exhibited lower BDI scores compared to those with less than 12 months of experience. Interestingly, the type of PA did not influence BDI or PSQI scores, suggesting that consistency and intensity are more critical than the kind of exercise itself. Conclusions: Systematic, high-intensity PA, especially for a prolonged period of time, is significantly associated with lower depressive symptoms. The exploratory nature of this study highlights training frequency and intensity as potential factors that need further research. These findings highlight the mind–body connection and demonstrate that PA might be an intervention supporting mental well-being.