From the Breast Oncology Program, University of Michigan Comprehensive Cancer Center, Ann Arbor, Michigan
Author's disclosure of potential conflicts of interest is found at the end of this article.
Address reprint requests to Daniel F. Hayes, MD, Clinical Director, Breast Oncology Program, University of Michigan Comprehensive Cancer Center, 1500 E. Medical Center Drive, Ann Arbor, MI 48109; e-mail: hayesdf{at}umich.edu
Overview: Morbidity and mortality from breast cancer have been reduced over the last four decades mainly because of improved therapies, which are frequently associated with life-threatening toxicities. Optimal application of systemic therapies should be directed toward delivering therapy that will be the most effective with the fewest side effects. There are three categories of tumor markers that may be helpful in selecting therapies for patients with breast cancer. Tumor tissue-based markers, such as estrogen receptor and human epidermal growth factor receptor (HER)-2, are already quite useful for selecting candidates for anti-estrogen and anti-HER2 therapies. Circulating markers, such as the soluble protein markers CA15–3, CA27.29, CEA, and extracellular domain of HER2, or circulating tumor cells may be valuable, especially in the metastatic setting. More recently, germline markers that provide insight into inherited differences in genes that encode for drug distribution enzymes or drug targets also may permit individualization of therapy.
