Differences In Expression Of PD-L1 Between Primary Breast Cancer And Postoperative Recurrence Metastasis And Its Impact On Prognosis

Background:The mechanism of tumor immune microenvironment has been a research focus in recent years.Immune escape plays a key role in tumor progression and development,especially the PD-1/PD-L1 pathway.Many studies have suggested that change in immune microenvironment are involved in the occurrence and development of triple negative breast cancer,but the relationship between tumor cell PD-L1 expression and clinical prognosis is still unclear.Some studies have found differences in the tumor microenvironment between primary tumors and metastatic tumors,but the mechanism of tumor microenvironment changes during breast cancer recurrence remains unclear.Purpose:This study aimed to evaluate the relationship between PD-L1expression and prognosis in breast cancer tumor cells.At the same time,we will study the differences in the expression of PD-L1 between the primary and recurrent foci of various molecular types of breast cancer in China,to provide a basis for the future selection of precise immunotherapy for breast cancer.Method:Data was collected from Medical record management system of the Second Affiliated Hospital of Nanchang University.54 female breast cancer patients who had underwent radical mastectomy from May 1,2011 to December 31,2018 in the hospital and had recurrence were selected.Through immunohistochemistry（Immunohistochemistry,IHC）,the 54 patients’samples were immunologically tested,50 of which met the conditions of this study.We evaluated the relationship between the expression of TILs and tumor cell PD-L1 in breast cancer primary tumors and their clinical characteristics and immune characteristics,and compare the immune microenvironment differences in primary breast cancer and metastases.Results:50 cases in total were included in this study.Each case was matched of a primary lesion and a metastasis,so 100 tumor tissue’s samples received ICH detection.The results suggested:Firstly,there were differences in PD-L1⁺TILs for different molecular types of breast cancer,PD-L1 expression of tumor cells,grade 3in lymphatic structure score,CD3⁺T cell count,and CD⁴⁺T cell count.The high expression of PD-L1⁺TILs was positively correlated with high tumor grade,positive PD-L1 expression in tumor cells,and high-grade tertiary lymphatic structure.Secondly,there were differences in the expression of PD-L1 in tumor cells for different tumor molecular types,tumor tissue classification,PD-L1 expression in DICS,TILs density score,PD-L1⁺TIL,tertiary lymphatic structure score,CD3⁺T lymphocyte count,CD4⁺T lymphocyte count,CD8⁺T lymphocyte count,CD20⁺B lymphocyte count,and FoxP3⁺T lymphocyte count.The positive expression of PD-L1 in tumor cells was positively correlated with high grade of tumor tissue,high density of TILs,and high expression of PD-L1⁺TIL;high score of tertiary lymphatic structure.Thirdly,the median DFS and median OS of positive tumor cell PD-L1group were lower than those of PD-L1 negative group,and the survival rate of PD-L1negative group was higher than that of PD-L1 positive group.PD-L1⁺TILs expression was not associated with prognostic survival.Fourthly,the expression of TILs,PD-L1⁺TILs,and tumor cell PD-L1 in the immune microenvironment of primary and recurrent breast cancer cells were different.TILs density,PD-L1⁺TILs density,and PD-L1 expression in tumor cells were lower than those in primary tumors.Conclusions:1.Tumor cell PD-L1 expression,PD-L1⁺TILs density,and TILs density in breast cancer recurrence and metastasis are lower than those in the primary focus,suggesting that immune escape plays a key role in breast cancer recurrence after surgery.2.The expression of PD-L1 in tumor cells is positively correlated with high grade of tumor tissue,high density of TILs,high density of PD-L1⁺TIL,and high score of tertiary lymphoid structure.3.The expression of PD-L1 in tumor cells is associated with poor DFS and OS,suggesting that this type of breast cancer is more malignant and has a worse prognosis.