Low Estrogen Receptor (ER)–Positive Breast Cancer and Neoadjuvant Systemic Chemotherapy: Is Response Similar to Typical ER-Positive or ER-Negative Disease?. Issue 1 (8th May 2018) - Landmann, Alessandra
Abstract: Objectives: Pathologic complete response (pCR) rate after neoadjuvant chemotherapy was compared between 141 estrogen receptor (ER)–negative (43%), 41 low ER+ (13%), 47 moderate ER+ (14%), and 98 high ER+ (30%) tumors. Methods: Human epidermal growth factor receptor 2–positive cases, cases without semiquantitative ER score, and patients treated with neoadjuvant endocrine therapy alone were excluded. Results: The pCR rate of low ER+ tumors was similar to the pCR rate of ER– tumors (37% and 26% for low ER and ER– respectively, P = .1722) but significantly different from the pCR rate of moderately ER+ (11%, P = .0049) and high ER+ tumors (4%, P < .0001). Patients with pCR had an excellent prognosis regardless of the ER status. In patients with residual disease (no pCR), the recurrence and death rate were higher in ER– and low ER+ cases compared with moderate and high ER+ cases. Conclusions: Low ER+ breast cancers are biologically similar to ER– tumors. Semiquantitative ER H-score is an important determinant of response to neoadjuvant chemotherapy.