Diindolylmethane in Treating Patients With Stage I or Stage II Prostate Cancer Undergoing Radical Prostatectomy

DISEASE CHARACTERISTICS: * Histologically or cytologically confirmed adenocarcinoma of the prostate * Stage I or II (T1-T2 a, b, or c) disease * Disease confined to the prostate by clinical judgment of the surgeon * Deemed an appropriate candidate for surgery by clinical judgment of the surgeon PATIENT CHARACTERISTICS: * ECOG performance status 0-2 * ANC ≥ 1,500/mm³ * Platelet count ≥ 100,000/mm³ * Hemoglobin ≥ 8.0 g/dL * Total bilirubin ≤ 1.5 times upper limit of normal (ULN) * AST and/or ALT ≤ 2.5 times ULN if alkaline phosphatase normal OR alkaline phosphatase ≤ 4 times ULN if AST and/or ALT normal * Serum creatinine ≤ 2.0 mg/dL * No history of allergic reactions attributed to compounds of similar chemical or biological composition to oral microencapsulated diindolylmethane * No concurrent uncontrolled illness including, but not limited to, any of the following: * Ongoing or active infection * Symptomatic congestive hart failure * Unstable angina pectoris * Cardiac arrhythmia * Psychiatric illness or social situation that would limit compliance with study requirements PRIOR CONCURRENT THERAPY: * No prior chemotherapy, hormonal therapy, brachytherapy, cryotherapy, external beam radiotherapy, or other therapy for prostate cancer * No concurrent micronutrient supplements or dietary soy products * No concurrent systemic therapy for any other cancer * No concurrent p450 inducers or inhibitors (e.g., carbamazepine, clarithromycin, fluconazole, fosphenytoin, itraconazole, ketoconazole, phenobarbital, phenytoin, rifabutin, or rifampin) * No concurrent finasteride or dutasteride * No other concurrent investigational or commercial agents or therapies for the malignancy