LAUSR

Purpose: To compare tumor response rates and survival outcomes between single and double hormone receptor (HR)‐positive breast cancer (BC) patients treated with neoadjuvant chemotherapy. Patients and Methods: A retrospective review was conducted using the Sunnybrook Biomatrix database to identify eligible patients. A multivariable logistic regression analysis was performed to assess the association between HR status (single/double HR+) and pathologic complete response (pCR) rates. A Kaplan‐Meier method was used to estimate recurrence‐free survival (RFS), and a log‐rank test was used to compare RFS between 3 subgroups: single or double HR+ and HR− patients. Results: Three hundred four BC patients were included in the analysis with a median follow‐up of 43.3 months (Q1‐Q3, 28.7‐61.1). Forty‐seven percent (47/101), 31% (11/36), and 14% (23/167) of patients with HR−, single HR+, and double HR+ disease experienced pCR, respectively. Patients' characteristics differed between single and double HR+ disease (age, human epidermal growth factor receptor 2, and nodal status). Only in univariate analysis were patients with single HR+ disease more likely than patients with double HR+ disease to experience a pCR (odds ratio = 2.6; 95% confidence interval, 1.14‐6.01; P = .02). However, this association did not remain significant in multivariable logistic regression analysis (odds ratio = 1.82; 95% confidence interval, 0.72‐4.56; P = .2). No difference in survival (RFS) was seen in the 3 subgroups: HR−, and single and double HR+ patients. Conclusion: Patients with single versus double HR+ BC have different tumor characteristics. Their outcome may differ in terms of pCR and survival. Prospective studies are needed to validate this conclusion, which may have treatment implications.