Impact of progesterone receptor status on response to neoadjuvant chemotherapy in estrogen receptor-positive breast cancer patients.

INTRODUCTION: Breast cancer patients respond differently to neoadjuvant chemotherapy(NAC) based on receptor subtype. The aim of this study was to assess the impact of progesterone receptor (PgR) status on response to neoadjuvant chemotherapy (NAC) in estrogen receptor (ER)+, human epidermal growth factor receptor (HER)- breast cancer patients. METHODS: ER+ and HER- patients receiving NAC over a 7-year period (2011-2017) were identified. The primary outcome was breast complete pathological response (pCR) rate. Secondary outcomes included axillary pCR, axillary/breast pCR and complete radiological response (cRR). RESULTS: A total of 203 patients were identified (149 in the ER+, PgR+, and HER- group and 54 in the ER+, PgR-, and HER- group). Compared with the PgR+ group, PgR- patients were significantly associated with breast pCR (31.5% vs 7.4%; χ² test; P < .01). In multivariable analysis, PgR- status (odds ratio [OR], 4.58; 95% confidence interval [CI]: 1.58,13.28; P = .005), radiological size >50 mm (OR, 5.38; 95% CI: 1.07,27.04; P = .04) and grade (OR, 3.52;95% CI: 1.21,10.23;P = .02) were significant predictors of breast pCR. Only PgR- status was a significant predictor of cRR (OR, 6.234; 95% CI: 2.531, 15.355; P < .001). In node positive patients, PgR negativity was associated with a trend towards breast/axillary nodal pCR (22% vs 12.7%; χ² test; P = .055). CONCLUSION: Over 30% of ER+, PgR-, and HER- patients will have a breast pCR after NAC. PgR- is the only significant predictor of breast pCR/cRR in this tumor subtype. ER+, PgR-, and HER- patients should be considered for NAC.