ESR1 and breast cancer: Olaparib treatment increased 3-year invasive disease-free survival by 19% in ER+/HER2- BC patients who received neoadjuvant chemotherapy, although the difference was not significant (86 vs. 67%, hazard ratio 0.52, 95% confidence interval 0.25–1.04), likely due to the small patient population (N = 196, 11% of all patients) [88].