Of a total of 242 men with Grade I-2 prostate cancer screened for the study between 2003–2005, only 53 men met the eligibility criteria and were consecutively admitted to the study. Men who were otherwise eligible, although recommended for active surveillance, opted for the more aggressive and evolving treatment options such as cryosurgery or seed implants in place of active surveillance. A total of 50 men completed the intervention and were able to provide complete data pretreatment and posttreatment, including serum and plasma for analysis. Of the subjects, 3 dropped out of the study, including 1 from the placebo group and 2 from the isoflavone-treated group. Reasons for dropping out of the study included noncompliance to study agent (1 subject) and Grade I to II AEs that resulted in 2 subjects not willing to continue and dropping out of the study. Thus, a 94.3% subject retention rate was achieved in the subjects recruited.
Initial comparison of baseline demographic variables such as age, race, anthropometrics measurements such as height, weight BMI, smoking history, family history of cancer, and personal history of BPH is displayed in . Although no significant differences were observed in the 2 groups on these variables, notably, over 50% of prostate cancer patients in both groups were former or current smokers and had a mean BMI >25. An increased number of subjects in the placebo group (78.6%) reported current or history of alcohol consumption compared to the placebo group (56.00%; P = 0.08).
Demographic Characteristics of Subjects at Baseline
Subjects in both groups reported similar average intake of macronutrients and micronutrients at baseline (). Although protein, fats, cholesterol, and percent fat intake increased slightly in the treatment group during the intervention, this was not reflected as significant changes in weight, as caloric intake remained stable. No significant changes in anthropometric variables such as weight and BMI were observed during the study period.
Change in Plasma Isoflavones at Month 1 and Month 3 by Group
Changes in plasma isoflavone levels (daidzein, glycitein, and genistein; ) at baseline, 4, and 12 wk were analyzed. Significant increases in plasma daidzein (P < 0.0001), glycitein (P < 0.0001), and genistein (P < 0.0001) were observed from baseline to 4 wk in the treatment group compared to the placebo group. Similarly, significant increases in plasma daidzein (P < 0.0001), glycitein (P = 0.01), and genistein (P < 0.0001) were observed from baseline to 12 wk in the treatment group compared to the placebo group. Compared to plasma isoflavones daidzein and genistein, changes in plasma glycitein were observed to be much lower, although significantly higher in the isoflavone-treated group compared to the placebo.
The baseline and final concentrations of serum free testosterone, SHBG, and total estradiol for the 2 groups are displayed in . Although greater mean reduction of serum-free testosterone was observed in subjects in the isoflavone-treated group compared to the placebo group, these changes between the 2 groups were not statistically significant for this duration of intervention (P = 0.3). We failed to observe an increase in serum SHBG levels in the treatment group, as hypothesized. Total estradiol decreased in both groups.
Change in Serum Steroid Hormone and SHBG Concentrations From Baseline to Postintervention by Groupa
Related and unrelated or potentially related gastrointestinal, metabolic, and constitutional categories of AEs were all Grades I to II events and were similar in the 2 groups and did not produce clinical toxicity, thus not requiring early stopping or discontinuation of the study agent. Previous clinical trials in men with prostate cancer have reported relatively minor side effects of chronic isoflavone treatment including symptoms related to estrogenic effects such as breast changes, lowered libido, and increased frequency of hot flashes (2
). Unlike earlier reports, no symptoms related to estrogenic effects at this dose and period of intervention were observed.