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. This evidence concerns the gene MKI67 and breast carcinoma.