The purpose of this project is to establish a repository of information and samples from breast cancer patients or those at high risk of developing breast cancer, who are initiating hormone therapy as part of standard clinical care or prevention. This repository will include patient reported outcomes and other questionnaires, information on medication use, data about adherence to the hormone therapy and tumor characteristics, including prospectively collected samples.

This research is being done to learn more about the side effects of breast cancer hormone therapy and if a person's genetic information may help us to develop a way to predict the side effects a patient may have and how best to treat them. In addition, the investigators hope to look at how the side effects from hormone therapy influence a patient's willingness to continue hormonal treatment.

Men and women being prescribed hormone therapies including Tamoxifen, Raloxifene (Evista), Anastrozole (Arimidex), Letrozole (Femara), or Exemestane (Aromasin), by their oncologist for either prevention of breast cancer or treatment of breast cancer may join.

The decision of which hormone therapy to receive is the decision of the patient and physician, this study will collect samples and patient-reported outcomes during this routine, standard of care and will not direct any treatment decisions or interventions in any way.

Inclusion Criteria:

• Male or female
• 18 years of age or older
• Physically and cognitively able to complete the questionnaires
• Meet one of the following categories: 1) Initiating hormonal therapy for breast cancer prevention. All patients planned to initiate hormonal therapy with either Tamoxifen, Raloxifene (Evista®), Anastrozole (Arimidex®), Letrozole (Femara®) or Exemestane (Aromasin®) are eligible; concomitant use of Zoladex or Lupron is permitted; 2) Patients with histologically proven ductal carcinoma in situ (DCIS/stage 0) or stage I-III invasive carcinoma of the breast that is estrogen (ER) and/or progesterone (PR) positive by immunohistochemical staining, who are considering one of the above listed SERMs or AIs. These patients must have completed any planned chemotherapy and local therapy (e.g., lumpectomy or mastectomy); however, enrollment/initiation of hormonal therapy on study may be done prior to completion of radiation and/or biologic therapy (e.g., trastuzumab) at the discretion of the treating team; or, 3) The patient is aware of the nature of her diagnosis, understands the study regimen, its requirements, risks, and discomforts, and is able and willing to sign an informed consent form.
• Patients transitioning from one hormonal agent listed above to another may be enrolled prior to initiation of the new medication.

Exclusion Criteria:

• N/A

Men and women being prescribed hormone therapies including Tamoxifen, Raloxifene (Evista), Anastrozole (Arimidex), Letrozole (Femara), or Exemestane (Aromasin), by their oncologist for either prevention of breast cancer or treatment of breast cancer may join.