Aromatase Inhibitors in Premenopausal Women with Breast Cancer: The State of the Art and Future Prospects

Approximately 11% of patients with breast cancer (BCA) are diagnosed before menopause, and because in most of those patients the tumour expresses a hormone receptor, treatment with endocrine interventions can be applied in any setting of disease (early or advanced). In the past, hormonal treatment consisted only of the estrogen receptor modulator tamoxifen, associated with luteinizing hormone–releasing hormone (LHRH); more recently, aromatase inhibitors (AIS) have come into widespread use. The AIS interfere with the last enzymatic step of estrogen synthesis in which androgens are converted into estrogens. Initially, the AIS were used alone in postmenopausal patients to prevent disease recurrence, but together with LHRH analogs, they can be used in premenopausal patients to produce better estrogen suppression than can be achieved with tamoxifen plus a LHRH analog. Using a systematic review of the scientific literature (prospective and retrospective studies), we set out to assess the efficacy of AIS compared with other endocrine therapy in various disease settings (neoadjuvant, adjuvant, metastatic).