The specific role of isoflavones in reducing prostate cancer risk.
OBJECTIVE
To evaluate the effectiveness of supplementing a group of early stage prostate cancer patients, with 60 mg of soy isoflavones in producing a change in hormonal and proliferative risk parameters that are implicated in prostate cancer promotion.


METHODS
Seventy six eligible prostate cancer patients with a Gleason score of 6 or below, between ages 50 and 80 were admitted and supplemented with soy isoflavones or placebo for a 12 week period and changes in PSA and steroid hormones were analyzed at baseline and post intervention.


RESULTS
Fifty-nine patients completed the 12-week intervention. Serum free testosterone was reduced or showed no change in 61% of subjects in the isoflavone group compared to 33% in the placebo group. Serum total PSA decreased or was unchanged in 69% of the subjects in the isoflavone treated group compared to 55% in the placebo group. However, we did not see an increase in SHBG levels. Nineteen percent of subjects receiving soy isoflavones reduced total PSA by two points or more during the intervention period.


CONCLUSIONS
These data suggest that supplementing early stage prostate cancer patients with soy isoflavones, even in a study of short duration, altered surrogate markers of proliferation such as serum PSA and free testosterone in a larger number of subjects in the isoflavone supplemented group than the group receiving placebo. The study establishes the need to explore further the effects of prolonged and consistent soy consumption, which could potentially delay onset of histologic disease in this patient population.
Kumar
Nagi B
NB
Department of Nutrition, H. Lee Moffitt Cancer Center & Research Institute, University of South Florida, Tampa, Florida, USA. kumar@moffitt.usf.edu
Cantor
Alan
A
Allen
Kathy
K
Riccardi
Diane
D
Besterman-Dahan
Karen
K
Seigne
John
J
Helal
Mohamad
M
Salup
Raoul
R
Pow-Sang
Julio
J
D000284:Administration, Oral; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis*; D019587:Dietary Supplements; D018450:Disease Progression; D006801:Humans; D007529:Isoflavones / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D010919:Placebos; D017430:Prostate-Specific Antigen / Q000032:analysis; D011471:Prostatic Neoplasms / Q000517:prevention & control*; D012307:Risk Factors; D013025:Glycine max / Q000737:chemistry; D013739:Testosterone / Q000097:blood
D014408:Biomarkers, Tumor; D007529:Isoflavones; D010919:Placebos; D013739:Testosterone; C065753:isoflavanone; D017430:Prostate-Specific Antigen