A short communication from researchers at Monash University in Australia suggests that red-clover derived isoflavones may help prevent the progression of prostate cancer by killing off some of the cancer cells.
The researchers said they had noted the epidemiological evidence which suggests a geographical basis for the incidence of prostate cancer and dietary factors, including isoflavone consumption, may be linked to this phenomenon.
They set up a non-randomised, non-blinded trial to study the effects of isoflavone supplements taken by men already diagnosed with prostate cancer. The effects of the supplements were studied after the men underwent radical prostatectomy surgery, and were compared with matched controls from archived tissue.
Before surgery, 20 men consumed 160 mg/day of red clover-derived dietary isoflavones, containing a mixture of genistein, daidzein, formononetin, and biochanin A. Serum prostate specific antigen (PSA), testosterone, and biochemical factors were measured, and clinical and pathological parameters were recorded.
The incidence of apoptosis (cell death) in prostate tumour cells from radical prostatectomy specimens was compared between 18 treated (with supplements) and 18 untreated control tissues. There were no significant differences between pre- and post-treatment serum PSA, Gleason score, serum testosterone, or biochemical factors in the treated patients.
However apoptosis in radical prostatectomy specimens from treated patients was significantly higher than in control subjects, and especially in regions of low to moderate-grade cancer (Gleason grade 1-3). No adverse events related to the treatment were reported.
"This report suggests that dietary isoflavones may halt the progression of prostate cancer by inducing apoptosis in low to moderate-grade tumours," concluded the researchers. They add that this could be one of the factors contributing to the lower incidence of clinically significant disease in Asian men (due to the soy-rich Asian diet).
"The assessment of new prostatic therapies aimed at increasing apoptosis should control for intake of dietary isoflavones," added the researchers. The study is published in the December 2002 issue of Cancer Epidemiology Biomarkers & Prevention.