These clinical findings indicated value for the allosteric mTOR inhibitors used alongside tamoxifen or aromatase inhibitors in advanced endocrine resistant tumours and there has been recent USA Food and Drug Administration approval for everolimus in combination with exemestane in ER+/HER2- metastatic breast cancer after non-steroidal aromatase inhibitor failure[28]. Here, CYP19A1 is linked to breast cancer.