Diindolylmethane in Treating Patients With Nonmetastatic Prostate Cancer That Has Not Responded To Previous Hormone Therapy

DISEASE CHARACTERISTICS:

Histologically proven adenocarcinoma of the prostate
Prostate specific antigen (PSA)-only failure after local therapy (surgery, radiation therapy, brachytherapy, or cryotherapy)

Rising PSA despite androgen-deprivation therapy with castrate levels of testosterone (< 50 ng/dL)

Two successive rising PSA levels at least 1 week apart
PSA ≥ 5 ng/mL
Patients with a history of combined hormonal therapy must continue luteinizing-hormone releasing-hormone agonist treatment but must demonstrate rising PSA after anti-androgen withdrawal
No evidence of distant metastasis by bone scan and CT scan
No known brain metastases requiring active therapy

PATIENT CHARACTERISTICS:

ECOG performance status ≤ 3
Life expectancy ≥ 12 weeks
Absolute neutrophil count ≥ 1,500/mm^3
Platelet count ≥ 100,000/mm^3
Hemoglobin ≥ 8.0 g/dL
Total bilirubin ≤ 1.5 times upper limit of normal (ULN)
SGOT and/or SGPT ≤ 2.5 times ULN AND alkaline phosphatase normal OR alkaline phosphatase ≤ 4 times ULN AND SGOT and/or SGPT normal
Creatinine clearance ≥ 60 mL/min OR creatinine normal
Fertile patients must use effective contraception

None of the following conditions within the past 6 months:

Myocardial infarction
Severe or unstable angina
Symptomatic congestive heart failure
Cerebrovascular accident or transient ischemic attack
Coronary/peripheral artery bypass grafting
No other severe acute or chronic medical or psychiatric condition or laboratory abnormality that would preclude study participation

PRIOR CONCURRENT THERAPY:

See Disease Characteristics
At least 28 days since prior radiotherapy
At least 28 days since prior investigational agents for treatment of prostate cancer
At least 4 weeks since prior flutamide
At least 6 weeks since prior bicalutamide
No other concurrent antineoplastic agents
No concurrent warfarin-related anticoagulants
No concurrent proton-pump inhibitor drugs for gastroesophageal reflux disease (e.g., rabeprazole, esomeprazole magnesium, lansoprazole, omeprazole, or pantoprazole sodium)

No concurrent micronutrient supplements or dietary soy products

One daily multivitamin allowed