Craig A. Bunnell, MD, MPH, MBA

The number of cancer patients and cancer survivors continues to increase rapidly amid predictions of a shortfall in physicians to care for them. In addition, newer cancer therapies have become increasingly complex and resource-intensive, compounding the impending workforce shortage. Simultaneously, the growing understanding of the biologic heterogeneity of cancer and the development of pharmacogenomics have opened up the possibility of personalized approaches to cancer diagnosis and treatment. Such personalization has been promulgated as a means of decreasing the cost of drug development, improving the efficacy of treatments, and reducing treatment toxicity. Although there have been notable successes, the fulfillment of these promises has been inconsistent. Providing care for future cancer patients will require the development of innovative delivery models. Moreover, new approaches to clinical research design, to the assessment of therapeutic value, and to the approval of and reimbursement for diagnostics and treatments are needed.

The majority of invasive breast cancer patients present with hormone receptor-positive disease, and modulation of estrogen receptor (ER) activation is an essential component of systemic adjuvant therapy for these women. While tamoxifen has traditionally been the primary adjuvant endocrine therapy for all ER-positive women, recent trials evaluating the use of aromatase inhibitors (AIs) have challenged this standard in postmenopausal women, and ongoing trials are examining the optimal use of endocrine therapy in younger women. Issues regarding the optimal approach to endocrine therapy in both pre- and postmenopausal women are examined in this review.