Selecting adjuvant endocrine therapy for breast cancer

This year alone, more than 215,000 women in the United States will be diagnosed with, and over 40,000 will die from, invasive breast cancer. Recently, mortality from female breast cancer has declined despite an increase in its incidence. This decline corresponds with improved screening for prompt tumor detection, and advances in the treatment of early disease. Of these, endocrine therapy has played a prominent role. For women with estrogen receptor (ER)-positive and/or progesterone receptor (PR)-positive breast cancers, endocrine therapy has proven to be a major component of adjuvant therapy, but it is not effective in women whose breast cancers lack ERs and PRs. The selective estrogen-receptor modulator (SERM) tamoxifen has been well established as safe and effective in the adjuvant care of both pre- and postmenopausal women with hormone-receptor-positive early breast cancer. For premenopausal women, ovarian suppression is an important option to be considered. Additionally, the aromatase inhibitors have recently demonstrated utility in postmenopausal women. The ideal sequencing of treatment with tamoxifen and/or an aromatase inhibitor is the subject of several ongoing studies. Factors involved in selecting an appropriate endocrine regimen have grown considerably over the past decade. It is becoming more important for those caring for women with breast cancer to fully understand the available endocrine treatment options and the prognostic and predictive factors available to help select the most appropriate treatment. The goal of this article is to assist clinicians in making decisions regarding adjuvant hormonal therapy and to provide information regarding available clinical trials. To achieve this, the therapeutic options for hormonal therapy will be reviewed, as will prognostic and predictive factors used in making decisions. Finally, four cases illustrating these difficult decisions will be discussed, with recommendations for treatment.