Author: Hussain M et al
Publication: Nutr Cancer 2003;47(2):111-7
Epidemiological data suggests that an increased soy intake is related to a reduced risk of prostate cancer . In vitro tests showed that soy isoflavone genistein induces apoptosis and inhibits growth of both androgen-sensitive and androgen-independent prostate cancer cells.
The aim of this study was to determine the clinical effects of soy isoflavones on prostate cancer cells. Test were conducted on 41 patients with prostate cancer who had rising serum prostate-specific antigen (PSA) levels. Patients were divided in 3 groups:
– Group 1: patients with newly diagnosed or untreated disease
– Group 2: patients with increasing serum PSA following local therapy
– Group 3: patients receiving hormone therapy.
The patients received twice daily 100 mg of soy isoflavone, Novasoy(R), during 3 to 6 months. Although there were no sustained decreases in PSA qualifying for a complete or partial response, stabilization of the PSA occurred in 83% of patients in group 2 and 35% of patients in group 2. There was a decrease in the rate of the rise of serum PSA in the whole group with rates of rise decreasing from 14% to 6% in group 2 and from 31% to 9% in group 3.
The serum genistein and daidzein levels were also monitored. Genistein levels increased from 0.11 to 0.65 microM and daidzein levels from 0.11 to 0.51 microM. There was no significant change in the levels of testosterone, IGF-1, IGFBP-3, or 5-OHmdU.
These data suggest that soy isoflavones may benefit some patients with prostate cancer.