Abstract: This application provides a method to identify genetic markers associated with increased sensitivity or resistance to hormonal therapies using an outlier analysis. More specifically, this application discloses that amplifications on chromosomes 8 and 17 are associated with increased proliferation and poor outcome in ER-positive breast cancer, and amplicons 17q21.33-q25.1, 8p11.2 and 8q24.3 may be responsible for higher proliferation and poor outcome in the setting of antiestrogen, in particular Tamoxifen, treatment clinically observed in a subset of ER-positive, HER2-negative breast cancers. The invention also provides use of the identified genetic markers in the development of targeted treatments for antiestrogen-resistant ER-positive breast cancers as well as in improving current methods of drug response prediction.

Abstract: This application provides a method to identify genetic markers associated with increased sensitivity or resistance to hormonal therapies using an outlier analysis. More specifically, this application discloses that amplifications on chromosomes 8 and 17 are associated with increased proliferation and poor outcome in ER-positive breast cancer, and amplicons 17q21.33-q25.1, 8p11.2 and 8q24.3 may be responsible for higher proliferation and poor outcome in the setting of antiestrogen, in particular Tamoxifen, treatment clinically observed in a subset of ER-positive, HER2-negative breast cancers. The invention also provides use of the identified genetic markers in the development of targeted treatments for antiestrogen-resistant ER-positive breast cancers as well as in improving current methods of drug response prediction.