The importance of distant metastases in hormone-sensitive breast cancer.

Breast cancer is a leading cause of cancer death in women worldwide. Survival from breast cancer is improving, but distant metastases remain the most common type of breast cancer recurrence, resulting in more than 40,000 deaths per year in the USA alone. Distant metastases are associated with the poorest outcomes when compared with loco-regional or contralateral recurrences and are also associated with greater health care costs and diminished quality of life. The risk of distant metastases increases with larger primary tumor size, lymph node positive cancer, higher tumor grade, and prior loco-regional recurrence. Yet, even patients with minimal risk factors may develop distant metastases. Thus, reducing the development of such relapses is an important goal in adjuvant therapy. As the development of distant metastases has been consistently associated with eventual mortality from breast cancer, a reduction in distant metastases may serve as a better surrogate marker for overall survival and provide earlier results from clinical trials testing new types of adjuvant therapy.