Soy isoflavone supplementation and biochemical recurrence after curative treatment for localized prostate cancer

Background: Despite an abundance of soy interventions, the effect of soy isoflavones prior to curative treatment for localized prostate cancer on biochemical recurrence has not been evaluated.;Objective: To determine if short-term supplementation with soy isoflavones prior to curative treatment delays or prevents biochemical recurrence in men with localized prostate cancer.;Design: Electronic medical record reviews were conducted in February 2013 to gather follow-up data on men (n = 86) previously enrolled in the Role of Isoflavones in Prostate Cancer study. Data collected included demographics, treatment modalities and complications, clinical and pathological staging, Gleason score, body mass index (BMI), comorbidities, prostate-specific antigen (PSA), PSA recurrence, time to recurrence, and death status. Fisher Exact test was used to compare rates of biochemical recurrence. Mann-Whitney U test was used to compare time to recurrence. Time to event analyses were performed using Kaplan-Meier plots with Log-rank test applied to assess statistical significance. Logistic regression analysis using PSA recurrence (yes/no) as a response was used adjusting for age and race.;Results: Sixty-six men were included in the final analysis. p < 0.05 was considered statistically significant. Overall rate of recurrence was 9%, with a rate of 9.3% in the soy group and 8.8% in the placebo group (p = 0.63). Mean time to recurrence overall was 33 ± 22 months, with 27 ± 26 months in the soy group and 40 ± 20 months in the placebo group (p = 0.53). There was no difference in survival times to biochemical recurrence or death between groups.;Conclusion: Short-term supplementation with soy isoflavones prior to curative treatment for localized prostate cancer was not found to significantly affect biochemical recurrence in this study.