Authors: Alexander Frans Christiaan Hulsbergen; An Claes, MD, PhD; Vasileios Kavouridis, MD; Claudine Nogarede; Ali Ansaripour, BS; Nancy Lin, MD; Timothy Smith; Joost Verhoeff, MD, PhD; Marike Broekman (Utrecht, Netherlands)

Introduction: Brain metastases (BMs) in breast cancer can differ from the primary tumor in terms of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) expression. The aim of this study was to describe the frequency of this receptor discordance and assess its impact on survival outcomes. Methods: An international multi-center cohort of patients who underwent neurosurgical resection for breast cancer BMs was created. Data were retrospectively collected on ER, PR and HER2 expression in primary tumors and BMs. Multivariable Cox Proportional Hazards Model was used to assess effects of discordance on survival outcomes. Results: Across four institutions, 167 patients were included, and 149 (89.2%) had data available on all receptors. Discordance in any receptor occurred in 49 (32.9%) of patients. Receptor-specific discordance rates were 27/165 (16.3%) for ER, 33/159 (20.8) for PR, and 16/156 (10.3%) for HER2. Discordance, in particular loss of receptor expression, was highly correlated with worse overall survival after adjusting for patient age and receptor profile of the BM (HR = 2.45; CI = 1.53 – 3.39; p = 0.0002). Conclusion: Breast cancer BMs frequently display a different ER, PR and HER2 expression when compared to their primary tumors, and this discordance is prognostically unfavorable. Our results highlight a benefit of obtaining BM tissue in this patient population.
Brainlab Neurosurgery Award