An on‐treatment Ki67 threshold for switching from neoadjuvant aromatase inhibitor therapy to neoadjuvant chemotherapy has been established, using data from a study of preoperative letrozole.9, 10 We also consider tumor volume when determining the responder or nonresponder status of patients, using measurements obtained not only by caliper measurement but also by more objective measurements (ie ultrasound, CT, or MRI). This evidence concerns the gene MKI67 and neoplasm.