Department of Urology and Andrology, Graduate School of Comprehensive Human Science, University of Tsukuba, Tsukuba, Ibaraki, Japan.Department of Strategic Investigation on Comprehensive Cancer Network, Research Center for Advanced Science and Technology, The University of Tokyo, Tokyo, Japan; Department of Pharmacoepidemiology, Graduate School of Medicine and Public Health, Kyoto University, Kyoto, Japan; Department of Urology, Iwate Medical University School of Medicine, Morioka, Iwate, Japan; Department of Urology, Graduate School of Medical Sciences, University of Kyushu, Fukuoka, Japan; Department of Urology, Kanazawa University Graduate School of Medical Science, Kanazawa, Ishikawa, Japan; Department of Urology, Nihon University School of Medicine, Tokyo, Japan; Department of Urology, Nara Medical University, Kashihara, Nara, Japan; Department of Urology, Teikyo University School of Medicine, Tokyo, Japan; Department of Urology, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan; Department of Epidemiology, Sapporo Medical University School of Medicine, Sapporo, Hokkaido, Japan; Yakult Central Institute for Microbiological Research, Kunitachi, Tokyo, Japan.
Our previous case-control study suggested that equol, a metabolite of isoflavone, has a preventive effect on prostate cancer. To examine the prostate cancer risk based on isoflavone intake and equol production, we conducted a phase II, randomized, double-blind, placebo-controlled trial of oral isoflavone (60 mg/day) for 12 months. The inclusion criteria were Japanese men between 50 and 75 years of age, a serum PSA level of 2.5-10.0 ng/mL, and a single, negative prostate biopsy within 12 months prior to enrollment. The study included 158 men in 8 Japanese centers. Their median age was 66.0 years (range: 50-75 years), and the numbers of equol producers and non-producers were 76 (48%) and 82 (52%), respectively. The majority of adverse events were mild or moderate in severity, and the scheduled intake of tablets was completed by 153 patients (96.8%). The PSA value showed no significant difference between before and after treatment. Of the 89 patients evaluated by central pathological review, the incidence of biopsy-detectable prostate cancer in the isoflavone and placebo groups showed no significant difference (21.4% vs. 34.0%, p=0.140). However, for the 53 patients aged 65 years or more, the incidence of cancer in the isoflavone group was significantly lower than that in the placebo group (28.0% vs. 57.1%, p=0.031). These results support the value of isoflavone for prostate cancer risk reduction. A large-scale phase III randomized study of isoflavone tablets in men with different hereditary factors and living environments is warranted.
Miyanaga N, Akaza H, Hinotsu S, Fujioka T, Naito S, Namiki M, Takahashi S, Hirao Y, Horie S, Tsukamoto T, Mori M, Tsuji H. Are you the author?
Reference: Cancer Sci. 2011 Oct 11. Epub ahead of print.