Studies on PD-L1 expression in breast cancer have gained importance in recent years, especially in triple-negative breast cancer (TNBC). Our aim was to analyze the differential expression of PD-L1 to explore its correlation with response to neoadjuvant chemotherapy (NACT) and patient survival. PD-L1 expression was evaluated immunohistochemically (Ventana SP263 clone kit) by staining tumor specimen. PD-L1 positivity was defined as membranous staining > 1%, > 5%, > 10%, and > 20% on either tumor cell (TC) and /or immune cell (IC). Fifty patients with locally advanced TNBC, who had a partial response to NACT, were included in the study. PD-L1 staining was observed in TCs in 25 patients (50%) and in ICs in 23 patients (46%) when PD-L1 > 1% was considered positive. Patients with PD-L1 positivity on ICs were more likely to respond to chemotherapy as measured by “MD Anderson Cancer Center Residual Cancer Burden Index” (14/22, 63.6% vs. 10/27, 37%, p = 0.064). The 5-year disease-free survival (DFS) and disease-specific survival (DSS) rates were 46.3% and 51.4%, respectively. A high (> 20%) tumoral PD-L1 positivity was associated with a better DFS and DSS. Studies in the literature mostly focused on PD-L1 expression in inflammatory cells. However, our results suggest that patients with a high PD-L1 expression on TCs were more likely to have a better outcome. Since patients with residual tumor burden who express PD-L1 on TILs were more likely to respond to NACT, an immune checkpoint inhibitor therapy in addition to NACT would be an important option for TNBC with locally advanced disease.

中文翻译：

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PD-L1表达对新辅助化疗后残留肿瘤负荷的三阴性乳腺癌患者的临床影响

近年来，对乳腺癌中 PD-L1 表达的研究越来越重要，尤其是在三阴性乳腺癌 (TNBC) 中。我们的目的是分析 PD-L1 的差异表达，以探讨其与新辅助化疗 (NACT) 反应和患者生存的相关性。PD-L1 表达通过染色肿瘤标本进行免疫组织化学评估（Ventana SP263 克隆试剂盒）。PD-L1 阳性定义为肿瘤细胞 (TC) 和/或免疫细胞 (IC) 的膜染色 > 1%、> 5%、> 10% 和 > 20%。该研究包括 50 名局部晚期 TNBC 患者，他们对 NACT 有部分反应。当 PD-L1 > 1% 被认为是阳性时，在 25 名患者 (50%) 的 TC 和 23 名患者 (46%) 的 IC 中观察到 PD-L1 染色。根据“MD 安德森癌症中心残余癌症负担指数”衡量，IC 上 PD-L1 阳性的患者更有可能对化疗产生反应（14/22，63.6% 对比 10/27，37%，p = 0.064）。5 年无病生存率 (DFS) 和疾病特异性生存率 (DSS) 分别为 46.3% 和 51.4%。高（> 20%）肿瘤 PD-L1 阳性与更好的 DFS 和 DSS 相关。文献中的研究主要集中在炎症细胞中的 PD-L1 表达。然而，我们的结果表明，在 TC 上具有高 PD-L1 表达的患者更有可能获得更好的结果。由于在 TIL 上表达 PD-L1 的残留肿瘤负荷患者更有可能对 NACT 产生反应，因此除了 NACT 之外的免疫检查点抑制剂治疗将成为局部晚期 TNBC 的重要选择。