ESR1 and breast cancer: Basically, these studies showed similar results to ours: Guarneri et al. found retrospectively in a cohort of 1,731 breast cancer patients treated with varying neoadjuvant anthracycline-based regimes that ER+/HER2+ carcinomas had a higher pCR rate than ER+/HER2- tumors (15.3% vs. 6%) [30].