Is there a correlation between estrogen receptor expression level and early breast cancer survival? A retrospective study.

Abstract

e12574 Background: The optimal cut-off of estrogen receptor (ER) positivity is still debatable; however, adjuvant hormonal therapy is usually given if ER expression is ≥ 1%. The present study aims to assess the clinicopathological features and survival outcomes of patients with low compared to high ER expression levels. Methods: In this retrospective, we checked non-metastatic hormonal receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer patients who presented to three hospitals in Egypt and Saudi Arabia between 2016 and 2019. Different clinicopathological factors and data on relapse were checked in patients’ medical records. These data were compared in patients with ER-Low (1–10%) vs. ER-High (>10%) expression levels. Results: We included 419 patients who met the eligibility criteria for the study. Only 3.3% of patients had ER-Low. Compared to the ER-high group, the ER-low expression group was more likely to have grade 3 tumours (64.3% vs. 21.0%, p = <0.0001) and PR-negative tumors (64.3% vs. 16.3%, p = <0.0001). Furthermore, younger age (≤ 50 years) was more frequent in the ER-Low group compared to ER-High patients (71.4% vs. 42.5%, respectively, p = 0.032). Likewise, ER-high patients were more likely to have high ER-staining intensity (74.1% vs. 0.0%, p<0.0001). Disease-free survival (DFS) was numerically improved in patients with ER-high, but without statistical significance. After adjustment of different clinicopathological prognostic factors, the DFS benefit in the ER-high group was more definite (hazard ratio (HR) = 3.59, 95%, confidence interval (CI) = 1.11–11.55, and p value = 0.032). Conclusions: A lower estrogen receptor expression level (varying from 1 to 10%) in hormone-positive early breast cancer patients is an uncommon pattern associated with more aggressive disease features at diagnosis. This group of patients had a lower DFS than those with a higher degree of estrogen receptor expression, although there was no statistically significant difference in OS.