The REDUCE Follow-Up Study: low rate of new prostate cancer diagnoses observed during a 2-year, observational, followup study of men who participated in the REDUCE trial.

PURPOSE: The primary objective of the REDUCE (REduction by DUtasteride of prostate Cancer Events) Follow-Up Study was to collect data on the occurrence of newly diagnosed prostate cancers for 2 years beyond the 4-year REDUCE study. MATERIALS AND METHODS: The 4-year REDUCE study evaluated prostate cancer risk reduction in men taking dutasteride. This 2-year observational study followed men from REDUCE with a clinic visit shortly after study conclusion and with up to 2 annual telephone calls during which patient reported data were collected regarding prostate cancer events, chronic medication use, prostate specific antigen levels and serious adverse events. No study drug was provided and all biopsies during the 2-year followup were performed for cause. The primary objective was to collect data on the occurrence of new biopsy detectable prostate cancers. Secondary end points included assessment of Gleason score and serious adverse events. RESULTS: A total of 2,751 men enrolled in the followup study with numbers similar to those of the REDUCE former treatment groups (placebo and dutasteride). Few new prostate cancers were detected during the 2-year followup period in either former treatment group. A greater number of cancers were detected in the former dutasteride group than in the former placebo group (14 vs 7 cases). No Gleason score 8-10 prostate cancers were detected in either former treatment group based on central pathology review. No new safety issues were identified during the study. CONCLUSIONS: Two years of followup of the REDUCE study cohort demonstrated a low rate of new prostate cancer diagnoses in the former placebo and dutasteride treated groups. No new Gleason 8-10 cancers were detected.

Clinical characteristics and pharmacokinetics of purified soy isoflavones: multiple-dose administration to men with prostate neoplasia.

A phase I clinical trial was conducted to determine the safety, pharmacokinetic parameters, and efficacy of orally administered isoflavones (genistein and daidzein, potential cancer chemotherapeutic agents) over a 3-mo period in men with prostate neoplasia. Twenty men, ages 40 and above, with stage B, C, or D adenocarcinoma of the prostate were treated with a multiple-dose regimen of a soy isoflavone formulation (delivering approximately 300 or 600 mg/day genistein and half this much daidzein) for 84 days. The delivered dose of isoflavones was more than 10-fold higher than that typically taken by prostate cancer patients. In men with prostate cancer, relatively minor side effects of chronic isoflavone treatment were observed including some estrogenic effects (breast changes, increased frequency of hot flashes). Serum dehydroepiandrosterone was decreased by 31.7% (P = 0.0004) at the end of treatment. Except for those subjects whose prostate-specific antigen (PSA) values were below 0.4 ng/ml, subjects had a history of increasing PSA levels prior to the trial. This increase continued during the trial both while on soy isoflavones and after treatment was discontinued. On average the rate of rise accelerated after soy isoflavones were discontinued, but that difference did not attain statistical significance. Genistein and daidzein were rapidly cleared from plasma and excreted in urine. Pharmacokinetic data for chronic dose administration were similar to single-dose administration for the isoflavones investigated except that we observed slightly longer circulation time for daidzein.

Lack of significant genotoxicity of purified soy isoflavones (genistein, daidzein, and glycitein) in 20 patients with prostate cancer.

BACKGROUND: Genistein may be useful in the prevention or treatment of prostate cancer; however, it causes genetic damage in cultured human cells. OBJECTIVE: The objective was to assess the potential genotoxicity of a purified soy unconjugated isoflavone mixture in men with prostate cancer. DESIGN: Twenty patients with prostate cancer were treated with 300 mg genistein/d for 28 d and then with 600 mg/d for another 56 d. In peripheral lymphocytes, DNA strand breaks were assessed as nuclear tail moment, chromosomal damage was assessed as micronucleus frequency (MF), and translocations of the MLL gene (11q23) were assessed by using fluorescence in situ hybridization. Values are also reported for 6 healthy men. The studies were performed under Investigational New Drug application no. 54 137 at a tertiary referral academic medical center. RESULTS: No changes in group average or individual nuclear tail moment and MF were observed. We observed a single elevated MF value in one subject that exceeded a clinical threshold set before we initiated the study. A significant decrease in average COMET tail moment was observed on day 28 relative to day 0. We detected no genistein-induced rearrangements of the MLL gene in the 3 subjects we studied with this technique. MF increased significantly in lymphocytes exposed in vitro to unconjugated genistein at concentrations > or = 100 micromol/L. Total genistein never exceeded a peak concentration of 27.1 micro mol/L, and unconjugated genistein never exceeded a peak concentration of 0.32 micromol/L. CONCLUSION: Although isoflavones are capable of inducing genetic damage in vitro, a similar effect was not observed in subjects treated with a purified soy unconjugated isoflavone mixture.