title: Effect of soy protein isolate supplementation on biochemical recurrence of prostate cancer after radical prostatectomy: a randomized trial.
abstract: OBJECTIVE
  Soy consumption has been suggested to reduce risk or recurrence of prostate cancer, but this has not been tested in a randomized trial with prostate cancer as the end point.
  
  
  OBJECTIVE
  To determine whether daily consumption of a soy protein isolate supplement for 2 years reduces the rate of biochemical recurrence of prostate cancer after radical prostatectomy or delays such recurrence.
  
  
  METHODS
  Randomized, double-blind trial conducted from July 1997 to May 2010 at 7 US centers comparing daily consumption of a soy protein supplement vs placebo in 177 men at high risk of recurrence after radical prostatectomy for prostate cancer. Supplement intervention was started within 4 months after surgery and continued for up to 2 years, with prostate-specific antigen (PSA) measurements made at 2-month intervals in the first year and every 3 months thereafter.
  
  
  METHODS
  Participants were randomized to receive a daily serving of a beverage powder containing 20 g of protein in the form of either soy protein isolate (n=87) or, as placebo, calcium caseinate (n=90).
  
  
  METHODS
  Biochemical recurrence rate of prostate cancer (defined as development of a PSA level of ≥0.07 ng/mL) over the first 2 years following randomization and time to recurrence.
  
  
  RESULTS
  The trial was stopped early for lack of treatment effects at a planned interim analysis with 81 evaluable participants in the intervention group and 78 in the placebo group. Overall, 28.3% of participants developed biochemical recurrence within 2 years of entering the trial (close to the a priori predicted recurrence rate of 30%). Among these, 22 (27.2%) occurred in the intervention group and 23 (29.5%) in the placebo group. The resulting hazard ratio for active treatment was 0.96 (95% CI, 0.53-1.72; log-rank P = .89). Adherence was greater than 90% and there were no apparent adverse events related to supplementation.
  
  
  CONCLUSIONS
  Daily consumption of a beverage powder supplement containing soy protein isolate for 2 years following radical prostatectomy did not reduce biochemical recurrence of prostate cancer in men at high risk of PSA failure.
  
  
  BACKGROUND
  clinicaltrials.gov Identifier: NCT00765479.
authors.affiliation: Department of Pathology, College of Medicine, University of Illinois at Chicago, Chicago, IL 60612, USA. boslandm@uic.edu
authors.forename: Maarten C
authors.initials: MC
authors.lastname: Bosland
authors.forename: Ikuko
authors.initials: I
authors.lastname: Kato
authors.forename: Anne
authors.initials: A
authors.lastname: Zeleniuch-Jacquotte
authors.forename: Joanne
authors.initials: J
authors.lastname: Schmoll
authors.forename: Erika
authors.initials: E
authors.lastname: Enk Rueter
authors.forename: Jonathan
authors.initials: J
authors.lastname: Melamed
authors.forename: Max Xiangtian
authors.initials: MX
authors.lastname: Kong
authors.forename: Virgilia
authors.initials: V
authors.lastname: Macias
authors.forename: Andre
authors.initials: A
authors.lastname: Kajdacsy-Balla
authors.forename: L H
authors.initials: LH
authors.lastname: Lumey
authors.forename: Hui
authors.initials: H
authors.lastname: Xie
authors.forename: Weihua
authors.initials: W
authors.lastname: Gao
authors.forename: Paul
authors.initials: P
authors.lastname: Walden
authors.forename: Herbert
authors.initials: H
authors.lastname: Lepor
authors.forename: Samir S
authors.initials: SS
authors.lastname: Taneja
authors.forename: Carla
authors.initials: C
authors.lastname: Randolph
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Schlicht
authors.forename: Hiroko
authors.initials: H
authors.lastname: Meserve-Watanabe
authors.forename: Ryan J
authors.initials: RJ
authors.lastname: Deaton
authors.forename: Joanne A
authors.initials: JA
authors.lastname: Davies
mesh_terms: D000368:Aged; D001628:Beverages; D019587:Dietary Supplements; D004311:Double-Blind Method; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000517:prevention & control*; D017430:Prostate-Specific Antigen / Q000097:blood; D011468:Prostatectomy; D011471:Prostatic Neoplasms / Q000097:blood / Q000517:prevention & control* / Q000601:surgery*; D012306:Risk; D030262:Soybean Proteins / Q000627:therapeutic use*; D016896:Treatment Outcome
chemical_list: D030262:Soybean Proteins; D017430:Prostate-Specific Antigen