Prediagnostic concentrations of plasma genistein and prostate cancer risk in 1,605 men with prostate cancer and 1,697 matched control participants in EPIC

Purpose: Data from prospective epidemiological studies in Asian populations and from experimental studies in animals and cell lines suggest a possible protective association between dietary isoflavones and the development of prostate cancer. We examined the association between circulating concentrations of genistein and prostate cancer risk in a case-control study nested in the European Prospective Investigation into Cancer and Nutrition. Methods: Concentrations of the isoflavone genistein were measured in prediagnostic plasma samples for 1,605 prostate cancer cases and 1,697 matched control participants. Relative risks (RRs) for prostate cancer in relation to plasma concentrations of genistein were estimated by conditional logistic regression. Results: Plasma genistein concentrations were not associated with prostate cancer risk; the multivariate relative risk for men in the highest fifth of genistein compared with men in the lowest fifth was 1.00 (95 % confidence interval: 0.79, 1.27; p linear trend = 0.82). There was no evidence of heterogeneity in this association by age at blood collection, country of recruitment, or cancer stage or histological grade. Conclusion: Plasma genistein concentration was not associated with prostate cancer risk in this large cohort of European men.