A phase II trial of a soy beverage for subjects without clinical disease with rising prostate-specific antigen after radical radiation for prostate cancer.
Our objective was to evaluate the tolerability and effect of a daily soy beverage in prostate cancer patients with biochemical failure after radiotherapy. Patients with rising prostate-specific antigen (PSA) after radical radiation for prostate cancer were instructed to consume 500 ml of soy beverage daily for 6 mo. Tolerability of the soy beverage and compliance were assessed. PSA doubling times before and after the consumption of soy were compared. Thirty-four subjects were enrolled; 5 withdrew before 1 mo of soy for reasons unrelated to soy consumption. All remaining 29 subjects were included in the analysis. Mean consumption of the assigned soy beverage was 93%. Mild gastrointestinal upset (38%) not affecting soy consumption was the commonest side effect. PSA showed a declining trend in 4 patients (13.8%), and there was a > 100% prolongation of PSA doubling time in 8 patients (27.6%). However, PSA doubling time also showed a 50% or more shortening in 5 patients (17.2%). In our cohort of North American subjects, 6 mo of a daily soy beverage was well tolerated and was associated with a declining trend or more than 2 times prolongation of PSA doubling time in 41% of subjects. Confirmatory studies are warranted.
Kwan
Winkle
W
B.C. Cancer Agency: Fraser Valley Centre, Surrey, British Columbia, Canada V3V 1Z2. wkwan@bccancer.bc.ca
Duncan
Graeme
G
Van Patten
Cheri
C
Liu
Mitchell
M
Lim
Jan
J
D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D007529:Isoflavones / Q000008:administration & dosage; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000473:pathology / Q000532:radiotherapy* / Q000628:therapy*; D041942:Soy Milk / Q000008:administration & dosage*; D013739:Testosterone / Q000097:blood; D017211:Treatment Failure
D007529:Isoflavones; D013739:Testosterone; D017430:Prostate-Specific Antigen