Breast cancer is the leading cause of women’s death among all cancers. The main reason associated with this is the development of metastasis and therapy-resistant breast carcinoma (BC), which pose the main challenge of oncology nowadays. Evidence suggest that these tumors seem to have inhibitory mechanisms that may favor their progression and surveillance. Cancer cells can evade antitumor T cell responses by expressing some immune inhibitory molecules such as the cytotoxic T-lymphocyte antigen-4 (CTLA-4), whose clinical meaning has emerged in the last few years and is poorly understood in the BC context. This systematic literature review aims at identifying studies on CTLA-4 expression in BC, and address what is known about its clinical meaning. A literature search was performed in PubMed and LILACS databases, using the MESH terms “breast cancer”; “CTLA-4 Antigen/antagonists and inhibitors”; and “Lymphocytes, Tumor-Infiltrating/immunology”, published in the last 10 years. In total, 12 studies were included in this review. Systematic review used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. Despite the small number of eligible studies, the literature reports some associations between CTLA-4 expression in the tumor microenvironment and worse BC outcomes, regardless of its molecular subtype. CTLA-4 expression in BC is a putative marker of clinical significance and a rationale therapeutic target in the emerging field of immunotherapy.

在所有癌症中，乳腺癌是女性死亡的主要原因。与此相关的主要原因是转移性和抗治疗性乳腺癌 (BC) 的发展，这是当今肿瘤学的主要挑战。有证据表明，这些肿瘤似乎具有可能有利于其进展和监测的抑制机制。癌细胞可以通过表达一些免疫抑制分子来逃避抗肿瘤 T 细胞反应，例如细胞毒性 T 淋巴细胞抗原 4 (CTLA-4)，其临床意义在最近几年出现，但在 BC 背景下却知之甚少。这篇系统的文献综述旨在确定关于 BC 中 CTLA-4 表达的研究，并说明其临床意义的已知内容。使用 MESH 术语“乳腺癌”在 PubMed 和 LILACS 数据库中进行了文献检索；“CTLA-4 抗原/拮抗剂和抑制剂”；和“淋巴细胞，肿瘤浸润/免疫学”，发表于过去 10 年。本综述共纳入 12 项研究。系统评价使用了系统评价和元分析的首选报告项目。尽管符合条件的研究数量很少，但文献报道了肿瘤微环境中 CTLA-4 表达与更差的 BC 结果之间存在一些关联，无论其分子亚型如何. CTLA-4 在 BC 中的表达是具有临床意义的推定标志物，也是新兴免疫治疗领域的合理治疗靶点。