Characteristics and Prognosis of Estrogen Receptor Low-Positive Breast Cancer.

Abstract

PurposeThe updated American Society of Clinical Oncology/College of American Pathologists guideline for estrogen receptor (ER) testing recommends that breast cancer with ER expression in 1–10% of tumor cells should be reported as ER-low positive (ERlow), although limited data are available on the overall benefits of endocrine therapy. We investigated the clinicopathological characteristics and clinical outcomes of ERlow breast cancer and to compare them with those of ER-negative (ERneg) and ER-high (> 10% of tumor cells, ERhigh) breast cancers.MethodsConsecutive patients with invasive breast cancer who underwent curative surgery between November 2007 and December 2014 were included. Clinicopathological characteristics and disease-free survival (DFS) of ERlow tumors were compared with those of ERneg and ERhigh tumors.ResultsOf the 2,309 cases included, 46 (2%), 643 (27.8%), and 1,620 (70.2%) were ERlow, ERneg, and ERhigh, respectively. ERlow tumors were associated with no special type of histology (p = 0.011), advanced pT (p = 0.017), pN (p = 0.009) and anatomic stages (p < 0.001), high grade (p < 0.001), negative/low progesterone receptor (PR) status (p < 0.001), human epidermal growth factor receptor 2 positivity (p < 0.001), high Ki-67 (p < 0.001), and recurrence (p = 0.006) compared to ERhigh tumors. DFS was significantly dependent on ER status, and ERlow tumors showed poorer DFS than ERhigh tumors (p = 0.001), however, there was no significant survival difference between ERlow and ERneg tumors. Furthermore, DFS in ERhigh patients was affected by hormone therapy (p < 0.001), while it was not affected in ERlow patients.ConclusionPatients with ERlow breast cancer have clinicopathological characteristics that differ from those with ERhigh tumors. Although this study was limited by the small sample size of the ERlow group, no benefit from hormone therapy was observed in the ERlow group compared with the ERhigh group.