Abstract 5289: The role of the immune system in lymph node positive ER+ breast cancer

Abstract

Abstract Estrogen receptor (ER) positive breast cancer (BC) accounts for 70% of BC diagnoses and is associated with a good outcome when treated with conventional therapies, including tamoxifen. However, there remains a sub-population of patients who undergo relapse within 10 years of diagnosis and do not respond well to standard therapies. While lymph node (LN) status is an important indicator of poor prognosis, additional information is needed to more accurately predict patients who will or will not relapse. Previous genomic studies from our lab have shown that immune response is an important feature of LN+ BCs that do not relapse. In addition, other studies have also examined the role of the immune system in ER+ BC, but due to varying study designs, it is unclear how immune response pertains to ER+ BC relapse. The goal of this project is to characterize immune response in ER+ BC by measuring levels of immune markers using immunohistochemistry (IHC) and RNA expression levels and comparing those to tumour characteristics. We have developed a cohort of retrospective ER+ BC patients with tumour samples available through the Hamilton Health Science tumour bank. Patients were selected for eligibility based on ER status, early stage disease, and having long term clinical follow-up. Clinical charts for each patient were reviewed and pathological, treatment, and outcome data were abstracted. Tumour blocks were obtained and sections stained for haematoxylin and eosin were marked for tumour boarders then used to construct Tissue microarrays (TMA) for IHC assays and RNA is to be extracted from each tumour block. 318 patient samples have been obtained that meet eligibility requirements. Among those, 163 are LN- and 110 are LN+, and the remainder have unknown LN status. Primary endpoint for this study is the development of distant metastasis. Roughly 10% of LN- patients developed distant metastasis within 10 years and roughly 20% of LN+ patients developed distant metastasis. In total, 14% of patients came to endpoint during the study period. TMAs were stained for pathological markers, including ER, PR, HER2, and Ki67 as well as immune markers such as CD8 and CD20. RNA expression levels for each of these were also determined and both were compared with clinical outcome. Here we present a retrospective cohort of ER+ BC patients with 10 years of clinical follow-up data that can be used for IHC and RNA analysis. Further, we have examined the association between immune response and prognosis in lymph node positive ER+ BC patients. Citation Format: Jessica G. Cockburn, Amy Gillgrass, Anita Bane. The role of the immune system in lymph node positive ER+ breast cancer. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 5289. doi:10.1158/1538-7445.AM2015-5289