This study is to examine the effects of menstrual cycle, hormone therapy, and the use of tamoxifen on Tc-99m sestamibi uptake.

Arm 1

Inclusion Criteria:

• age 35-45
• have regular menstrual cycles as defined by having menstrual cycle length of 25-31 days, with menstrual flow of 2-7 days, and no intermenstrual spotting or bleeding.
• have had a negative screening mammogram within one year prior to the MBI studies that is available for comparison.

Exclusion Criteria:

• currently using any exogenous hormones (e.g., hormonal contraceptives, sex steroid hormones) or any estrogen receptor modulating drugs (e.g., tamoxifen, raloxifene) or any aromatase inhibitors
• have a personal history of any cancer, except non-melanomatous skin cancer
• unable to understand and sign the consent form
• pregnant or lactating
• physically unable to sit upright and still for 30 minutes

Arm 2

Inclusion Criteria:

• scheduled to begin one of the following regimens of HT:
• Any dosage of any formulation of systemic estrogen therapy in the setting of a prior hysterectomy
• Any dosage of continuous estrogen plus monthly, cyclic progesterone therapy where the progesterone therapy is the oral, micronized formulation
• had a negative screening mammogram within one year prior to the MBI studies that is available for comparison.

Exclusion Criteria:

• have a personal history of any cancer, except non-melanomatous skin cancer
• unable to understand and sign the consent form
• pregnant or lactating
• physically unable to sit upright and still for 30 minutes

Arm 3

Inclusion Criteria:

• scheduled to begin treatment with tamoxifen Or are currently being treated with tamoxifen (for > 1 month) and have had an MBI scan performed prior to its initiation
• have had or will have the following test performed at Mayo Clinic: #87966, Cytochrome P450 2D6 genotyping for Tamoxifen Hormonal Therapy
• have had a screening or diagnostic mammogram within one year of the MBI studies that is available for comparison.

Exclusion Criteria:

• are using or have used any exogenous hormones (e.g., hormonal contraceptives, sex steroid hormones), any estrogen receptor modulating drugs other than tamoxifen, or any aromatase inhibitors from the time of 1 month prior to the first MBI until completion of the second MBI.
• have been treated or will be undergoing treatment with systemic chemotherapy or external radiation beam therapy to the breast from the time of 6 months prior to the first MBI until the completion of the second MBI.
• unable to understand and sign the consent form
• pregnant or lactating
• physically unable to sit upright and still for 30 minutes

Community Sample