The vast majority of studies investigating immune checkpoint inhibition (ICI) in patients with breast cancer have focused on triple-negative breast cancer (TNBC). In this study, we compared the tumor immune microenvironment (TIME) between TNBC and hormone receptor-negative HER2-positive breast cancer based on a selection of immune markers at the protein level in an institutional retrospective series. Additionally, we performed a similar comparison using publicly available transcriptomics data. Altogether, the results show a comparable TIME in both groups, with possible implications for the use of ICI in patients with hormone receptor-negative HER2-positive breast tumors.

Introduction: Recent data show that a subgroup of patients with breast cancer might benefit from immune checkpoint blockade (ICB). However, adequate biomarkers to select patients for ICB are lacking. A better understanding of the immune microenvironment of breast cancer is paramount in the quest for appropriate biomarkers. We investigated several immune related parameters in hormone receptor negative breast cancer, attempting to characterize the tumor microenvironment. We observed the immune micro-environment from three angles. Firstly, we counted and further characterised stromal tumour infiltrating lymphocytes (sTILs). Secondly, we measured the expression of PD1 and PD-L1. Lastly, the expression of CD73 on tumor cells, a potential regulatory molecule of immune escape, was analysed. Methods: Resection specimens of 198 patients, diagnosed with ER/PR negative invasive adenocarcinoma of > 2 cm between 2005 and 2010, were analysed. TILs percentages were analysed according to the international guidelines. Immunohistochemical (IHC) analyses of CD3, CD4, CD8, CD68, CD73, FoxP3 and PD1 were assessed. PD-L1 IHC assay and interpretation was performed by QualTek and a modified proportion score (MPS) was used. The immune parameters were correlated with clinicopathological parameters. Results: Clinicopathological characteristics are summarized in Table 1. The median expression of the immune parameters ranges from 0 to 10 and is presented in Table 2. Further, sTIL percentages were categorised into three groups, with 10% and 30% as cut-off, which matches with respectively 31%, 50% and 19% of the patients. Applying a cut-off of 1%, only 17% of the samples showed PD-L1 expression while 97% of the samples showed PD-1 expression on TILs. As could be expected a significant positive association was observed between sTILs and CD3, CD4 and CD8, but also with CD68, FoxP3 and PD-L1. No association could be noted between PD-1 expression and any of the other parameters. When taking patient age into account, older patients have significant less sTILs and expression of CD3, CD4, CD8 and FoxP3. An increase in the fraction of sTILs with 10% was significantly associated with a lower risk of metastasis ([HR] = 0.529, p < 0.01). This also reflects in the observation that an increase in CD3, CD8 and FoxP3 lowers the risk of metastasis ([HR] of respectively 0.940 (p < 0.01), 0.876 (p = 0.02) and 0.658 (p = 0.01)). No significant association between CD73 and the risk of metastasis was observed (p = 0.1098). Table 1: Clinicopathological informationAge (mean)56,36  N%Histological typeNon special type16382,32Special type3517,68 Molecular type Triple negative14271,72HER2 positive5628,28 Tumour grade 110,512115,56318693,94pT217487,8832311,62410,51pN09748,9917638,382136,573126,06 Table 2: Expression of the different immune parametersVariableMedian (%)IQR (%)Range (%)sTILs105 - 305 - 80CD3105 - 205 - 70CD455 - 55 - 20CD855 - 105 - 60CD68105 - 205 - 80CD7300 - 50 - 90FoxP321 - 20 - 10PD-155 - 50 - 30PD-L100 - 00 - 100 Conclusion: The expression of immune parameters is this cohort of patients was rather low. Only 19% have high number of sTILs (>30%) and PD-L1 expression (>1%) was present in 17% of patients. Moreover, the number of sTILs as well as subtypes of lymphocytes decreases with age. Further, our data show a significant positive association between sTILs, subtypes of lymphocytes (CD3, CD4, CD8, FoxP3), macrophages (CD68) and PD-L1. Lastly, high sTIL count, expression of CD3, CD8 and FoxP3 were associated with a decreased risk of metastasis. Citation Format: Hanne Vos, Kathleen Lambein, Giuseppe Floris, Bram Mariën, Lieze Berben, Patrick Neven, Hans Wildiers, Ines Nevelsteen, Ann Smeets. Characterization of the tumor microenvironment in a large series of ER/PR negative breast cancer [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P5-04-23.

The non-invasive prenatal test (NIPT) is a highly sensitive blood analysis tool that allows for the early detection of multiple chromosomal abnormalities, including Down syndrome. Prenatal testing in general and a positive test outcome in particular leave pregnant parents facing difficult ethical decisions and life-changing dilemmas. The language used by medical practitioners in this context has the potential to exert a strong influence on parents in their decision-making process. During counseling, health care professionals (HCPs) are expected to encourage parents to make an informed yet autonomous decision, which hinges on maximally unbiased, clear and consistent communication from the HCP. It is still unclear whether medical students are aware of this importance of unbiased communication, how they perceive the role of HCPs in the prenatal counseling process, and what perspectives they have regarding the disabilities screened for. Our research project aims to address this gap, presenting the results of a transdisciplinary survey completed by 245 medical students at KU Leuven. In particular, the survey investigates: (1) the students' view on the ideal prenatal counseling process; (2) their knowledge of NIPT and Down syndrome (the most prevalent disability NIPT screens for); and (3) their general attitudes towards disabilities. Results reveal that more than 50% of medical students do not feel prepared for genetic counseling. The survey further shows a lack of knowledge and some clearly negative attitudes towards life with disability; 20% of medical students agree that a life with Down syndrome should be avoided. Overall, results indicate fairly heterogeneous distribution of knowledge and fairly diverse attitudes of the students, suggesting revisions in the current curriculum might be needed to increase the homogeneity towards counseling and disabilities in the medical student population.