ESR1 and breast cancer: In both subgroups, pCR was associated with long-term outcome (5-year iRFS 100% for pCR versus 50% for residual disease and 89.5% for pCR versus 51.6% for residual disease in the ER 1–9% and ER < 1% subgroups, respectively) and relapses occurred early, mostly in the first 3 years after BC diagnosis (Fig. 2).