New developments in hormone receptor-positive disease.

Of more than one million women diagnosed with breast cancer each year, approximately 700,000 have hormone receptor (HR)(+) disease. Although endocrine therapy has revolutionized breast cancer management and substantially improved outcomes in these patients, the optimal management of these patients remains a significant challenge. For instance, the threshold for adding adjuvant chemotherapy is a topic of continuing debate, and the most effective regimens that include endocrine therapy and chemotherapy are still under debate as well. Tumor markers, such as Ki-67, and host markers, such as cytochrome P450 2D6, are being studied as potential tools to offer more tailored adjuvant endocrine therapy. Current research suggests that luminal A and luminal B cancers are two completely different diseases, and work is being performed to better distinguish between these two disease types and deliver more effective therapy to individual patients. This article addresses these important outstanding issues with respect to HR(+) disease.