Phase II Trial of Isoflavone in prostate specific antigen recurrent prostate cancer after previous local therapy
Data exist that demonstrate isoflavones have potent antiproliferative effects on prostate cancer cells. We evaluated the efficacy of isoflavone in patients with PSA recurrent prostate cancer after prior therapy.
We postulated that isoflavone therapy would slow the rate of rise of serum PSA.
Methods: Twenty patients with rising PSA after prior local therapy were enrolled in this open-labeled, Phase II, nonrandomized trial.
Patients were treated with 47 mg of isoflavonoid per 8 oz serving three times per day for 12 months. Serum PSA, testosterone, lipids, isoflavone levels (genistein, daidzein, and equol), and quality of life (QOL) were measured at various time points from 0 to 12 months.
PSA outcome was evaluated.
Results: Within the mixed regression model, it was estimated that PSA had increased 56% per year before study entry and only increased 20% per year for the 12-month study period (p = 0.05).
Specifically, the slope of PSA after study entry was significantly lower than that before study entry in 6 patients and the slope of PSA after study entry was significantly higher than before study entry in 2 patients. For the remaining 12 patients, the change in slope was statistically insignificant.
Nearly two thirds of the patients were noted to have significant levels of free equol in their serum while on therapy.
Conclusion: Dietary intervention with isoflavone supplementation has biologic activity in men with biochemical recurrent prostate cancer as shown by a decline in the slope of PSA.
This study provides additional support to the literature that nutritional supplements have biologic activity in prostate cancer and therefore, further, studies with these agents in randomized clinical trials should be encouraged.The study is registered at www.clinicaltrials.gov (registration # NCT00596895).
Author: John M Pendleton, Winston W Tan, Satoshi Anai, Myron Chang, Wei Hou, Kathleen T. Shiverick and Charles J. Rosser
Credits/Source: BMC Cancer 2008, 8:132
Published on: 2008-05-12
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