Effect of soy phytoestrogens on hot flashes in postmenopausal women with breast cancer: a randomized, controlled clinical trial.
OBJECTIVE
Vasomotor symptoms, such as hot flashes and night sweats, in breast cancer survivors are often worsened by chemotherapy and tamoxifen, and/or the discontinuation of hormone replacement therapy at diagnosis. This study evaluated the acceptability and effectiveness of a soy beverage containing phytoestrogens as a treatment for hot flashes in postmenopausal women with breast cancer.


METHODS
A randomized, placebo-controlled, double-blind clinical trial was conducted in postmenopausal women with moderate hot flashes who were previously treated for early-stage breast cancer. Women were stratified for tamoxifen use and randomized to a soy beverage (n = 59) containing 90 mg of isoflavones or to a placebo rice beverage (n = 64). Women recorded the number and severity of hot flashes daily with a daily menopause diary for 4 weeks at baseline and for 12 weeks while consuming 500 mL of a soy or placebo beverage.


RESULTS
There were no significant differences between the soy and placebo groups in the number of hot flashes or hot flash scores. However, presumably because of a strong placebo effect, both groups had significant reductions in hot flashes. Mild gastrointestinal side effects were experienced by both groups but occurred with greater frequency and severity with soy. The mean serum genistein concentration at 6 weeks was significantly higher in women who consumed soy (0.61 +/- 0.43 micromol/L) compared with placebo (0.43 +/- 0.37 micromol/L) (P =.02). Overall acceptability and compliance were high and similar in both groups.


CONCLUSIONS
The soy beverage did not alleviate hot flashes in women with breast cancer any more than did a placebo. Future research into other compounds is recommended to identify safe and effective therapies for hot flashes in breast cancer survivors.
Van Patten
Cheri L
CL
British Columbia Cancer Agency, Vancouver Cancer Centre, Vancouver Hospital and Health Sciences Centre, and University of British Columbia, Vancouver, British Columbia, Canada. cvpatten@bccancer.bc.ca
Olivotto
Ivo A
IA
Chambers
G Keith
GK
Gelmon
Karen A
KA
Hislop
T Gregory
TG
Templeton
Edith
E
Wattie
Angela
A
Prior
Jerilynn C
JC
D001943:Breast Neoplasms / Q000150:complications*; D004311:Double-Blind Method; D004968:Estrogens, Non-Steroidal / Q000627:therapeutic use*; D005260:Female; D019584:Hot Flashes / Q000188:drug therapy* / Q000209:etiology; D006801:Humans; D007529:Isoflavones; D008875:Middle Aged; D048789:Phytoestrogens; D028321:Plant Preparations; D017698:Postmenopause; D013025:Glycine max / Q000737:chemistry; D016896:Treatment Outcome
D004968:Estrogens, Non-Steroidal; D007529:Isoflavones; D048789:Phytoestrogens; D028321:Plant Preparations