Çetin, KenanKökten, ŞerminSarıkamış, BaharYıldırım, SedatGökçe, Oruç NumanBarışık, Nagehan ÖzdemirKılıç, Ülkan2024-02-102024-02-102024Çetin, K., Kökten, Ş., Sarıkamış, B., Yıldırım, S., Gökçe, O. N., Barışık, N. Ö., & Kılıç, Ü. (2024). The association of PD-L1 expression and CD8-positive T cell infiltration rate with the pathological complete response after neoadjuvant treatment in HER2-positive breast cancer. Breast Cancer Research and Treatment, 1–11. https://doi.org/10.1007/s10549-023-07242-10167-68061573-7217https://doi.org/10.1007/s10549-023-07242-1https://hdl.handle.net/20.500.12428/5644Purpose: Achieving a pathological complete response (pCR) after neoadjuvant therapy in HER2-positive breast cancer patients is the most significant prognostic indicator, suggesting a low risk of recurrence and a survival advantage. This study aims to investigate clinicopathological parameters that can predict the response to neoadjuvant treatment in HER2 + breast cancers and to explore the roles of tumour-infiltrating lymphocytes (TILs), CD8 + T lymphocytes and PD-L1 expression. Methods: This single-centre retrospective study was conducted with 85 HER2-positive breast cancer patients who underwent surgery after receiving neoadjuvant therapy between January 2017 and January 2020. Paraffin blocks from these patients were selected for immunohistochemical studies. Results: A complete pathological response to neoadjuvant treatment was determined in 39 (45.9%) patients. High Ki-67 index (> 30%), moderate to high TIL infiltration, PD-L1 positivity and high CD8 cell count (≥ 25) were significantly associated with pCR in univariate analyses (p: 0.023, 0.025, 0.017 and 0.003, respectively). Multivariate regression analysis identified high Ki-67 index (> 30%) and CD8 cell infiltration as independent predictors for pCR in HER2-positive breast cancer. Conclusions: High Ki-67 index, and high CD8 cell count are strong predictors for pCR in HER2-positive breast cancer. Tumours with high Ki-67 index, high TILs and CD8 infiltration may represent a subgroup where standard therapies are adequate. Conversely, those with low TILs and CD8 infiltration may identify a subgroup where use of novel strategies, including those that increase CD8 infiltration could be applied.eninfo:eu-repo/semantics/openAccessCD8HER2 + breast cancerNeoadjuvant therapyPD-L1ResponseArticle10.1007/s10549-023-07242-1Q2WOS:0011497463000032-s2.0-8518301708738273215