Adjuvant Endocrine Therapy of Perimenopausal and Recently Postmenopausal Women With Hormone Receptor-Positive Breast Cancer

Although 5 years of tamoxifen has been the standard adjuvant endocrine therapy for premenopausal women with hormone receptor-positive breast cancer for more than 2 decades, emerging results suggest that either switching to an aromatase inhibitor after 5 years of tamoxifen when postmenopausal or continuing tamoxifen for an additional 5 years can further decrease relapse risk. As a result, more premenopausal breast cancer patients will be continuing adjuvant endocrine therapy through the menopause transition. In this setting, questions arise regarding continued tamoxifen use through 10 years and/or the timing and appropriateness of switching to an aromatase inhibitor. In addition, it is now recognized that estrogen levels substantially decline for approximately 2 years after the last menstrual period and that chemotherapy and/or tamoxifen-induced amenorrhea preclude reliable ovarian function determination. Because aromatase inhibitors are only effective in a low estrogen environment without ovarian estrogen production, determination of the optimal endocrine adjuvant therapy for perimenopausal women and those recently postmenopausal represent a challenge requiring understanding of current clinical study results and the potential for interactions among therapeutic interventions, ovarian function, and clinical outcome. Available options include tamoxifen for 10 years, tamoxifen for 5 years followed by aromatase inhibitors, tamoxifen with a luteinizing hormone-releasing hormone (LHRH) agonist, aromatase inhibitor with an LHRH agonist or aromatase inhibitor with bilateral oophorectomy. Although completed (Austrian Breast Cancer Study Group [ABCSG]-12) and ongoing (SOFT [Suppression of Ovarian Function Trial], TEXT [Tamoxifen and Exemestane Trial]) clinical trials are addressing some issues, many questions will remain requiring individualized clinical judgement. Rationale supporting the available endocrine therapy options in this setting and recommendations for clinical management follow. (C) 2014 Elsevier Inc. All rights reserved.