 The purpose of our study is to recruit and treat 96 men diagnosed with prostate cancer and scheduled for a prostatectomy with a capsule form of either purified isoflavones or placebo for a 3-6 week period to see if we can slow down the rate of prostate cancer growth. A placebo is a pill or something that looks like the medicine that is being studied but has no active medicine in it. We also want to see if taking purified isoflavones is safe and if it reduces lower urinary tract symptoms. In addition, we want to study if purified isoflavones are able to slow the progression of prostate cancer, and the mechanism of action of purified isoflavones. If the safety and the effects of purified isoflavones on slowing down the progression of prostate cancer is shown in our study, this will also be a safe way of treating men who are at high risk of prostate cancer, so that we can prevent prostate cancer in the future. 