The sequential use of endocrine treatment for advanced breast cancer: Where are we?

Background: Hormone receptor-positive advanced breast cancer is an increasing health burden. Although endocrine therapies are recognised as the most beneficial treatments for patients with hormone receptor-positive advanced breast cancer, the optimal sequence of these agents is currently undetermined. Methods: We reviewed the available data on randomised controlled trials (RCTs) of endocrine therapies in this treatment setting with particular focus on RCTs reported over the last 15 years that were designed based on power calculations on primary end points. Results: In this paper, data are reviewed in postmenopausal patients for the use of tamoxifen, aromatase inhibitors and fulvestrant. We also consider the available data on endocrine crossover studies and endocrine therapy in combination with chemotherapy or growth factor therapies. Treatment options for premenopausal patients and those with estrogen receptor-/human epidermal growth factor receptor 2-positive tumours are also evaluated. Conclusion: We present the level of evidence available for each endocrine agent based on its efficacy in advanced breast cancer and a diagram of possible treatment pathways.