MKI67 and breast cancer: Our main objectives were to investigate, in postmenopausal patients with ER‐positive breast cancer and Ki67 index ≤30%, first, the efficacy and safety of neoadjuvant endocrine therapy with exemestane alone; and second, the efficacy and safety of subsequent neoadjuvant chemoendocrine therapy with exemestane in combination with low‐dose cyclophosphamide in patients who do not respond to exemestane monotherapy.