Chemoprevention trials in men with prostate-specific antigen failure or athigh risk for recurrence after radical prostatectomy: Application to efficacy assessment of soy protein

This article discusses the basic elements of chemoprevention trial designs using cohorts of men following radical prostatectomy who either have prosta te-specific antigen (PSA) failure indicative of recurrence or are at high r isk for recurrence (positive surgical margins, extracapsular extension, sem inal vesicle invasion, positive lymph nodes, Gleason score of greater than or equal to 8, preoperative serum PSA less than 20 ng/mL). Two ongoing rand omized, double-blind, placebo-controlled clinical trials with soy protein a s intervention in these 2 populations are described. In the trial with men at high risk for recurrence, participants started intervention within 4 mon ths after surgery and were followed for up to 2 years; primary endpoints we re PSA failure rate and time-to-PSA failure. In the trial with men with PSA failure (PSA 0.1 to 2.0 ng/mL), participants received treatment for 8 mont hs and the primary endpoint is rise in PSA over time. The strengths and lim itations of these designs are discussed and interim experience using studie s with soy protein as the intervention agent are summarized.