The Management of ER-Low, HER2-Negative Breast Cancer in the United Kingdom: A Survey of Current Clinical Practice

Abstract

Introduction: The optimal management of oestrogen receptor (ER)-low HER2-negative breast cancer (BC) is unclear. We surveyed current approaches of UK clinicians in ER-low BC, and also present outcomes of ER-low early BC at single centre. Methods: Survey: We conducted an anonymised online survey of clinicians treating BC in the UK between 6 May and 5 June 2024. Participants were presented with clinical scenarios of ER-low (Allred ER3/ER4) BC with multiple-choice and free-text questions. Clinical audit: Patients diagnosed with stage I–III, ER2–4 HER2-negative BC undergoing neoadjuvant treatment (chemotherapy vs. chemo-immunotherapy) from 1 January 2017 to 31 December 2023 were included. Clinical data was collected retrospectively at Barts Health NHS Trust, London, UK. The primary endpoint was pathological complete response (pCR). Results: Survey: Of 72 survey respondents, 40% recommended neoadjuvant chemo-immunotherapy for ER3 disease vs. 10% for ER4 disease; 57% recommended adjuvant endocrine therapy for ER3 disease, and 90% for ER4 disease. In the advanced setting 75% recommended chemo-immunotherapy for PD-L1-positive ER3 disease with 7% recommending CDK4/6 inhibitors. For PDL1-positive ER4 disease, these percentages were 32% and 51% respectively. In PDL1-negative disease, chemotherapy rates were 81% for ER3 and 36% for ER4 disease. Clinical audit: Sixty-six patients receiving neoadjuvant treatment were included, with 29 belonging to the ER2, 30 belonging to the ER3 and 7 belonging to the ER4 groups respectively; 33% received neoadjuvant chemo-immunotherapy. pCR rate was 61%, with no association with ER score for chemotherapy (p = 0.319) and chemo-immunotherapy (p = 0.603). Conclusions: There is marked variation in approach to ER-low in the UK. The audit data suggests treating ER-low BC as triple-negative BC.