Abstract 2806: Progression of ductal carcinoma in situ (DCIS), is it in the immune microenvironment
Authors: Almekinders Mathilde M. , Visser Lindy , Thijssen Bram , Linden Rianne van der , Rooijen Charlotte van , Kristel Petra , Broeks Annegien , Bismeijer Tycho , Wessels Lodewyk , Hooijberg Erik , Visser Karin de , Lips Esther , Wesseling Jelle ,   on behalf of the PRECISION team (PREvent ductal Carcinoma In Situ Invasive Overtreatment Now)
Published: August 2019

Abstract
Introduction: DCIS is a non-obligate precursor to invasive breast cancer (IBC). DCIS patients are treated similarly to breast cancer with surgery, often followed by radiotherapy and/or endocrine treatment. However, most DCIS lesions will never progress to IBC, indicating that overdiagnosis and overtreatment exists. DCIS lesions show variable amounts of immune cells, particularly in the periductal stroma. Immune escape might be a critical step for transition from DCIS to IBC. We aim to identify factors within the immune microenvironment of DCIS lesions that distinguish harmless from potentially hazardous DCIS.
Methods: A case-control study is being conducted consisting of women with pure DCIS diagnosed between 1989-2005 with median follow-up of 12 years, treated with breast conserving surgery only. Cases are defined as women with DCIS developing subsequent ipsilateral breast cancer (iIBC), controls as women with DCIS without subsequent iIBC. Multispectral immunohistochemical imaging was performed on primary DCIS lesions, aiming at detection of CD20+ B-cells, CD8+ T-cells, CD3+ T-cells, CD3+Foxp3+ regulatory T-cells, and CD68+ macrophages. Density of immune cell subsets in cells/mm2, immune cell ratios and spatial relationships were calculated for 27 cases and 28 controls. These immune cell related factors were correlated to outcome and integrated with RNAseq data of pure microdissected DCIS. We performed gene set enrichment analysis on the correlation between DCIS gene expression and density of immune cell types with sample permutation (flexgsea R package).
Results: Stromal lymphocyte, B-cell, CD8+ T-cell, regulatory T-cell and macrophage density did not significantly differ between cases and controls. Immune cell composition (CD8+ T-cell/lymphocyte, CD8+ T-cell/CD3+Foxp3+ regulatory T-cell and CD20+/lymphocyte ratio) and fraction of regulatory T-cells in close proximity of a CD8+ T-cell did not differ between cases and controls. We find a negative association between stromal B-cell density and DCIS gene expression of estrogen receptor (ESR1) targets. Higher stromal T-cell density was associated with proliferation and expression of genes characteristic for luminal B and basal-like subtypes. Furthermore, higher density of specific immune cell subsets within the DCIS compartment was associated with several immune and cancer pathways.
Conclusion: A first set of analyzed DCIS cases (n=27) and controls (n=28) show no significant differences regarding immune cell density, composition and spatial relationships. Considering the entire group of DCIS patients (n=55), a negative association between stromal B-cell density and gene expression of ESR1 targets was found. Higher density of lymphocytes was associated with proliferation and expression of genes characteristic for luminal B and basal-like subtypes. The full set of 175 DCIS lesions will be presented at AACR Annual Meeting 2019.
Citation Format: Mathilde M. Almekinders, Lindy Visser, Bram Thijssen, Rianne van der Linden, Charlotte van Rooijen, Petra Kristel, Annegien Broeks, Tycho Bismeijer, Lodewyk Wessels, Erik Hooijberg, Karin de Visser, Esther Lips, Jelle Wesseling, on behalf of the PRECISION team (PREvent ductal Carcinoma In Situ Invasive Overtreatment Now). Progression of ductal carcinoma in situ (DCIS), is it in the immune microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2806.