Inclusion Criteria

DISEASE CHARACTERISTICS:

- Meets 1 of the following criteria:

- Prior diagnosis of infiltrating carcinoma of the breast ≥ 5 years prior to study
entry

- Prior diagnosis of ductal carcinoma in situ

- No evidence of disease

- Completed all cancer therapy, with the exception of reconstructive surgery, at least
6 months prior to study entry

- Meets one of the following criteria:

- Normal mammogram within 1 year of study entry

- Underwent bilateral mastectomy and has been in remission for 5 years, as
documented by an oncologist

- Hormone receptor status not specified

PATIENT CHARACTERISTICS:

- ECOG performance status 0-1

- WBC ≥ 3,500/mm³

- ANC ≥ 1,500/mm³

- Platelet count ≥ 100,000/mm³

- Hemoglobin ≥ 9.0 g/dL

- Postmenopausal, defined as any of the following:

- Continuous absence of menstruation for 12+ months

- Status post bilateral oophorectomy

- Status post hysterectomy with follicle-stimulating hormone in menopausal range

- Creatinine ≤ 1.5 times upper limit of normal (ULN) or less

- Total bilirubin ≤ 1.5 times ULN

- AST and ALT < 2 times ULN

- No allergy to mushrooms

- No personal history of any invasive cancer, other than breast cancer, or squamous
cell or basal cell skin cancer

- No osteoporosis, defined as a bone-mineral density T-score of < -2.5 on dual-energy
x-ray absorptiometry scan

- No major systemic infections or other major medical illnesses of the cardiovascular,
respiratory, or digestive system

PRIOR CONCURRENT THERAPY:

- See Disease Characteristics

- More than 3 months since prior and no concurrent hormone-modifying medications,
including any of the following:

- Oral contraceptives

- Hormone replacement

- Selective estrogen receptor modifiers

- Other aromatase inhibitors

- Gonadotropic-releasing hormone modifiers

- At least 1 month since prior and no other concurrent mushroom extracts or DHEA as a
dietary supplement

- No concurrent therapy, except continued medications for unrelated illness that are
not excluded, and necessary medications for unrelated acute illnesses that may occur
during the study (e.g., cold, flu, or infection)

- No more than 3 concurrent servings per week of the following foods:

- Flaxseeds and flaxseed meal

- High-energy bars or diet bars containing soy or soy protein

- Liquid-nutrition drinks containing soy or soy protein (e.g., Odwalla Future
Shake or Ensure Plus)

- Miso soup

- Natto

- Packaged mixed dishes with soy or tofu (e.g., lasagna, burritos, or stir-fry)

- Cooked soybeans or edamame (i.e., green soybeans)

- Roasted soy nuts

- Soymilk, regular or low-fat, plain or flavored

- Soy cheese, such as cheddar, mozzarella, cram cheese, or parmesan (includes all
foods made with soy cheese)

- Soy protein powders (e.g., performance or body-builder powders)

- Soy yogurt, all types

- Soy sauce, tamari, teriyaki sauce, Szechuan sauce, or hoisin sauce

- Soy ice cream, tofutti, or other soy desserts

- Tempeh, all types

- Tofu, all types, including low-fat, flavored, marinated, and smoked

- Tofu or soy breakfast sausage, bacon, or other breakfast meat

- Tofu or soy cold cuts, hot dogs, or other deli meat substitutes

- Veggie soy or tofu burger, ground meat substitute (texturized vegetable
protein), or soy or tofu, chicken, or turkey

- Concurrent supplemental calcium and/or vitamin D and bisphosphonates allowed provided
doses remain constant throughout the run-in and treatment portions of the trial