ESR1 and breast cancer: However, we previously reported that 10% of ER is an ideal threshold to predict the pathological complete response (pCR) to the neo-adjuvant chemotherapy (NACT), time-to-recurrence or death, showing that patients with ER < 1% and patients with ER 1%–10% had similar short-term clinical outcomes (pCR rates of 26.3% and 28.1%, respectively) among patients with HER2-negative breast cancer; only patients with ER > 10% had survival benefits from adjuvant hormonal therapies [7].