Brief Summary: RATIONALE: Genistein may stop the growth of tumor cells by blocking some of the enzymes needed for cell growth. PURPOSE: This randomized phase II trial is studying how well genistein works in treating patients with prostate cancer.

Detailed Description: PRIMARY OBJECTIVES: I. Determine whether genistein treatment will decrease the number of circulating prostate cells (CPCs) in the peripheral blood as measured by qRT-PCR for PSA performed on RNA extracted from peripheral blood mononuclear cells (PBMNCs). SECONDARY OBJECTIVES: I. Determine the natural history of circulating prostate cells (CPCs) in a cohort of subjects prior to and post radical prostatectomy. II. Compare the measurement of PSA between three separate methods: in CPCs by qRT-PCR, in serum by the standard clinical chemistry assay (i.e., ELISA), and in plasma and serum by the nano-PSA assay. III. Measure the effect of genistein on gene and protein expression in prostate tissue by qRT-PCR and immunohistochemistry, respectively, for the following genes and their respective protein products: HSP27, MMP-2, ALK-2, BASP1, and HCF2. OUTLINE: Patients are randomized to 1 of 2 treatment arms. ARM I: Patients receive oral genistein once daily for 3 months beginning at least 1 month prior to radical prostatectomy. ARM II: Patients receive oral placebo once daily for 3 months beginning at least 1 month prior to radical prostatectomy. All patients undergo radical prostatectomy at least 2 weeks, but not more than 3 months following the start of therapy. After completion of study treatment, patients are followed at 1, 6, and 12 months.