The specific role of isoflavones in reducing prostate cancer risk.
aDepartment of, Nutrition, FL, United States, bDepartment of Cancer Control &, cDepartment of Surgery; H. Lee Moffitt Cancer Center & Research Institute, Universtiy of South Florida, Tampa, FL, United States
To evaluate the effectiveness of supplementing a group of early-stage prostate cancer patients with 60 mg soy isoflavones to produce changes in hormonal and proliferative risk variables that are implicated in prostate cancer promotionMETHODS: Seventy-six eligible prostate cancer patients with a Gleason score of six or below, aged 50 and 80 y, were admitted and supplemented with soy isoflavones(60 mg/d) for 12 wk. Changes in proliferative and hormonal biomarkers were analyzed at baseline and postintervention, RESULTS: Of the 76 subjects, 59 completed the 12-wk intervention. Serum free testosterone was reduced or showed no change from baseline to the end of the study in 61% of the subjects in the isoflavone group compared with 33% in the placebo group. Serum total prostate-specific antigen (PSA) decreased or was unchanged in 69% of the subjects in the isoflavone group compared with 55% in the placebo group. However, we did not see an increase in levels of sex hormone binding globulin. Nineteen percent of subjects receiving soy isoflavones reduced total PSA by 2 points or more during the intervention period CONCLUSIONS: These data suggest that surrogate markers of proliferation such as serum total PSA and free testosterone are reduced in a larger number of subjects in the isoflavone-supplemented group compared with the group receiving placebo even in a study of short duration (12 wk). Thus prolonged consistent isoflavone use may interfere with disease progression or delay the onset of histologic disease.
Paper presented at the International Symposium on Predictive Oncology and Intervention Strategies; Nice, France; February 7 - 10, 2004; in poster session 997 (Chemoprevention).