DISEASE CHARACTERISTICS:

• At increased risk of developing breast cancer in ≥ 1 previously unaffected breast, as defined by any of the following:

  • Estimated 5-year risk of developing breast cancer using the Gail model, as defined by 1 of the following:

    • Gail score ≥ 1.66%
    • Gail score ≥ 0.1% for women age 20-29 years
    • Gail score ≥ 1.0% for women age 30-39 years

  • Estimated 5-year risk of developing breast cancer using the Claus model

    • Claus score ≥ 1.66%
    • Claus score ≥ 0.1% for women age 20-29 years
    • Claus score ≥ 1.0% for women age 30-39 years
  • Prior diagnosis of unilateral in situ or invasive breast cancer OR history of atypical hyperplasia
  • BRCA 1 and/or BRCA 2 positivity
  • History of lobular carcinoma in situ
• No evidence of breast cancer, as determined by a negative mammogram within the past 6 months and a history and physical
• No previously diagnosed breast cancer unless all systemic therapy (including endocrine therapy) was completed at least 1 year ago

PATIENT CHARACTERISTICS:

• Female patient
• Pre- or postmenopausal
• ECOG performance status 0-1
• Hemoglobin > 10.0 g/dL
• Platelet count > 100,000/mm^3
• Absolute neutrophil count > 1,000/mm^3
• Creatinine < 2.0 mg/dL
• SGPT < 82 U/L
• SGOT < 68 U/L
• Bilirubin < 3 mg/dL* NOTE: * Patients with a higher level of bilirubin due to a familial metabolism may be eligible at the discretion of the investigator
• Life expectancy > 2 years
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective barrier contraception
• Must be willing to keep a dietary diary
• No venous thrombosis within the past year
• No known soy intolerance
• No unrecognized or poorly controlled thyroid disease
• No other cancer within the past 5 years except nonmelanomatous skin cancer or noninvasive cervical cancer
• No other medical condition that, in the opinion of the investigator, would jeopardize either the patient or the integrity of the data obtained

PRIOR CONCURRENT THERAPY:

• See Disease Characteristics

• None of the following for ≥ 2 weeks before the first random fine needle aspiration and during study participation:

  • Oral contraceptives
  • Soy supplements
  • High soy-containing foods
  • Fish oil supplements
  • Multivitamins
  • Vitamins C and E
  • Daily aspirin or nonsteroidal anti-inflammatory drugs
• No other concurrent investigational agents
• No concurrent warfarin or other blood thinners