The evolving role of endocrine therapy for early stage breast cancer

Abstract

With the completion of these clinical trials evaluating the integration of AIs in the adjuvant treatment of breast cancer, there are several questions that remain unanswered: (1) What constitutes the optimal endocrine therapy; (2) what is the optimal duration of therapy; (3) what is the optimal sequencing of endocrine agents? It has become obvious from these trials that five years of tamoxifen therapy alone is not optimal adjuvant treatment; the addition of an AI at some point during the course of therapy should be recommended. However, whether the AI should be given as initial treatment or sequenced with tamoxifen remains to be defined. An updated technology assessment developed by the American Society of Clinical Oncology (ASCO) was made available in early 200552). The ASCO panel recommends the following general guidelines for use of aromatase inhibitors: Postmenopausal women with hormone receptor-positive breast cancer may substitute an aromatase inhibitor for tamoxifen as initial adjuvant therapy. Alternatively, women can still begin treatment with tamoxifen and plan to switch to an aromatase inhibitor after two to five years. It is not clear at this time which strategy is superior. Postmenopausal women who are currently taking tamoxifen may consider switching to an aromatase inhibitor after two to five years of tamoxifen therapy. Women who switch to an aromatase inhibitor may continue this therapy for two to three more years but no longer than five years. Women are advised that the result of treatment with an aromatase inhibitor for longer than five years has not been studied and should only be done in the context of a clinical trial. There are no data to recommend taking tamoxifen after an aromatase inhibitor.