ESR1 and breast cancer: In ER+ HER2− BC treated with anastrozole and palbociclib in the neoadjuvant setting, Bagegni et al. showed that the sensitivity and specificity of the decrease in serum TKa to predict tumor Ki-67 reduction in response to palbociclib were 94.1% (95%CI [86.2–100%]) and 84% (95%CI [69.6–98.4%]), respectively.