Genistein in Preventing Breast or Endometrial Cancer in Healthy Postmenopausal Women

You may be eligible if

• DISEASE CHARACTERISTICS:
• Healthy participants
• * Papanicolaou test (pap smear) normal within the past 13 months
• * Mammogram normal within the past 13 months
• No history of breast cancer
• Not at high-risk (5-year risk \< 1.9%) for breast cancer according to NCI's Breast Cancer Risk Assessment Tool
• Hormone receptor status:
• * Not specified
• PATIENT CHARACTERISTICS:
• Age
• 45 to 70
• Sex
• Female
• Menopausal status
• Postmenopausal
• * Last spontaneous menstrual bleeding \> 12 months ago
• Performance status
• ECOG 0-2
• Life expectancy
• Not specified
• Hematopoietic
• WBC ≥ 3,500/mm\^3
• Platelet count ≥ 100,000/mm\^3
• Hepatic
• Bilirubin ≤ 2.0 mg/dL
• ALT and AST \< 2 times normal
• No significant abnormality of the liver by physical exam
• Renal
• Creatinine \< 2.0 mg/dL
• Cardiovascular
• No significant cardiac disease
• No New York Heart Association class III or IV heart disease
• No significant abnormality of the heart by physical exam
• Pulmonary
• No significant abnormality of the lung by physical exam
• Other
• Body mass index \< 35
• Follicle-stimulating hormone \> 27 mIU/mL
• Thyroid or endocrine function test normal
• Alcohol intake ≤ 2 drinks/day or ≤14 drinks/week
• Not pregnant
• No intermediate equol values (≥10 ug/L to ≤ 20 ug/L) on soy challenge
• No history of seizures
• No significant abnormality of the spleen or other abdominal organs by physical exam
• No neurologic abnormality by physical exam
• No significant metabolic abnormality on the biochemical screen
• No history of substance abuse or addiction
• No tobacco use
• No diets containing \> 20 mg of genistein/day or \> 40 mg isoflavone/day
• No known intolerance to soy
• No other serious medical illness
• No active malignancy or malignancy initially diagnosed within the past 2 years except curatively treated nonmelanoma skin cancer
• PRIOR CONCURRENT THERAPY:
• Biologic therapy
• Not specified
• Chemotherapy
• More than 2 years since prior chemotherapy
• No concurrent chemotherapy
• Endocrine therapy
• More than 3 months since prior hormonal or estrogen therapy
• More than 3 months since prior tamoxifen or other selective estrogen-receptor modulators
• More than 1 month since prior supplements containing phytoestrogens or that have estrogenic side effects (soy isoflavones or PC-SPECS)
• No concurrent thyroid medication
• * Other concurrent endocrine medication allowed provided medication was initiated ≥ 3 months before study entry AND participant has been on a stable regimen for the past 3 months
• Radiotherapy
• Not specified
• Surgery
• No prior hysterectomy or oophorectomy
• Other
• More than 3 months since prior antibiotics