Endocrine Therapy in Treating Patients With HER2 Negative, Low Risk Breast Cancer

Inclusion Criteria

• •Able to provide written informed consent
• •A diagnosis of invasive breast cancer, with or without an in situ component, that is:
• •* Originally identified by screening mammography
• •* Characterized by standard diagnostic mammography +/- breast ultrasound
• •* Clinically node negative
• •* Confirmed by breast magnetic resonance imaging (MRI) in a facility that maintains active American College of Radiology (ACR) accreditation to be of low clinical stage (=\< 2 cm, node negative, unifocal invasive)
• •* Estrogen receptor (ER) and progesterone receptor (PR) Allred scored, each \> 5/8
• •* Her2 negative using American Society of Clinical Oncology (ASCO)-College of American Pathologists (CAP) guidelines
• •* ki-67 proliferation scored, \< 20%
• •* Clinical Nottingham grade 1 or 2
• •* Scored on the MammaPrint 70-gene breast cancer recurrence assay as low risk
• •Prior to the discovery of the breast cancer, clinically post-menopausal as defined as: i) one or more years from last menses; or ii) history of oophorectomy; or iii) follicle stimulating hormone (FSH) test result in the post-menopause reference range
• •Willing to accept oral endocrine therapy with a third generation aromatase inhibitor (AI) or selective estrogen receptor modifier (SERM)
• •Willing to undergo routine surveillance with breast ultrasound and/or mammography