We aim to compare the sensitivity of mammography to the sensitivity of Molecular Breast Imaging (a new gamma-camera based breast imaging technology) in women with dense breast tissue who are at increased risk for breast cancer.

The sensitivity of conventional mammography (MMO) is poor in women with mammographically dense breast parenchyma. We have developed Molecular Breast Imaging (MBI) - a new technique which utilizes a Cadmium-Zinc-Telluride (CZT) gamma camera for scintimammography that has a high sensitivity (~90%) for the detection of breast cancers independent of breast density.

The aim of this study is to demonstrate the utility of MBI as an adjunct screening modality for the detection of occult breast cancers in women with mammographically dense breast tissue. Initial recruitment will be from the pool of patients awaiting a screening mammogram in the Department of Radiology at Mayo Clinic Rochester. All patients will have a screening MMO and an MBI study. Patients with positive studies (MBI or MMO) will undergo additional diagnostic studies. At 15 months post-recruitment, all patients will be contacted by phone or mail to determine whether subsequent to their study, there has been any change in their breast status.

Inclusion Criteria:

1. Past prior screening mammography (SM) interpreted as negative or benign (This screening must have been performed at Mayo Clinic Rochester, Minnesota).

2. Past prior SM interpreted as heterogeneously dense or extremely dense (This screening must have been performed at Mayo Clinic Rochester, Minnesota).

3. Women younger than 50 years who had not undergone prior mammography, as most of these women have dense breasts.

4. Subjects had to have at least one of the following risk factors:

   1. Known mutation in breast cancer susceptibility gene 1 (BRCA1) or breast cancer susceptibility gene 2 (BRCA2)
   2. History of chest, mediastinal, or axillary irradiation
   3. Personal history of breast cancer
   4. History of prior biopsy showing atypical ductal hyperplasia, atypical lobular hyperplasia, lobular carcinoma in situ, or atypical papilloma
   5. Gail or Claus model lifetime risk greater than or equal to 20%
   6. Gail model 5 year risk greater or equal to 2.5%
   7. Gail model 5 year risk greater or equal to 1.6%
   8. One first-degree relative with history of breast cancer
   9. Two second-degree relatives with history of breast cancer

Exclusion Criteria:

1. They are unable to understand and sign the consent form
2. They are pregnant or lactating
3. They are physically unable to sit upright and still for 40 minutes.
4. They have self-reported signs or symptoms of breast cancer (palpable mass, bloody nipple discharge, axillary mass etc.).
5. They have had needle biopsy within 3 months, or breast surgery within 1 year prior to the study.
6. They are currently taking tamoxifen, evista (raloxifene), or an aromatase inhibitor for adjuvant therapy or chemoprevention.

Participants were followed for adverse events while they were on the study.