The purpose of this study to gather information about changes in the bones after stopping treatment with aromatase inhibitor/AI and denosumab. The study team will collect information from 5 standard clinic visits over the course of 24 months. The information will include information about participant health assessments, blood test results, and imaging results. After 24 months, participation in this study will be complete.

Inclusion Criteria:

• Women with confirmed diagnosis of breast cancer
• Participant must be post-menopausal, defined as last menstrual cycle at least 12 months prior to enrollment
• Received at least 2 doses of denosumab and then discontinued therapy
• Discontinued AI prior to or within 6 months of last denosumab injection
• Patients must be 18 years of age or olde

Exclusion Criteria:

• Patients with history of osteoporosis prior to starting denosumab, based on previous dual-energy X-ray absorptiometry (DEXA) scan;
• Patients with history of insufficiency fracture.
• Patients who continue treatment with a different bone modifying agent (i.e oral or intravenous bisphosphonates) after discontinuation of denosumab
• Patients on chronic low-dose glucosteroids.

Patients will be recruited through the Breast Medicine and Survivorship Services. Members of the research team will verify eligibility against the patient's medical record. Once eligibility is confirmed, and if the treating investigator has no objection to enrolling the patient in the research study, the patient will be approached for consent. Consent to the protocol will be conducted by a trained consenting professional. Consent will take place either in the clinic, or by following the most updated standard working procedures for consent via telemedicine.

Memorial Sloan Kettering Cancer Center supports the international committee of medical journal editors (ICMJE) and the ethical obligation of responsible sharing of data from clinical trials. The protocol summary, a statistical summary, and informed consent form will be made available on clinicaltrials.gov when required as a condition of Federal awards, other agreements supporting the research and/or as otherwise required. Requests for deidentified individual participant data can be made beginning 12 months after publication and for up to 36 months post publication. Deidentified individual participant data reported in the manuscript will be shared under the terms of a Data Use Agreement and may only be used for approved proposals. Requests may be made to: crdatashare@mskcc.org.