In cases of prostate cancer, especially when radiation and surgery have failed, it is common to use hormonal manipulation to manage and control prostate cancer. In late-stage prostate cancer, some men elect orchiectomy (removal of the testicles) as a permanent ablative approach whereas others choose chemical castration using luteinizing hormone releasing hormone (LHRH) agonists. LHRH is released from the hypothalamus of the brain when the hypothalamus detects dropping levels of testosterone. LHRH agonists can lead to a drop in testosterone by as much as 90 to 95%, to what is called castrate level.
As a prostate cancer treatment, the removal of testosterone from the body will temporarily stop or slow the growth and spread of the disease. However, vasomotor symptoms (i.e., hot flashes and night sweats) occur in approximately 80% of men who undergo hormone manipulation.
With this background in mind, and the knowledge that soy isoflavones alleviate hot flashes in women, researchers from several universities and clinics in the United States evaluated the effects of an isoflavone-rich soy protein (20 g providing 160 mg isoflavones) alone and in combination with venlafaxine, an anti-depressant that has been shown to alleviate hot flashes in women.
In all, 120 men age 46 to 91 years participated in this 12-week study. Unfortunately, neither venlafaxine nor soy protein alone or in combination had a significant effect on hot flash symptom severity score. However, soy protein improved measures of the quality of life. More specifically, soy led to improvements in emotional and functional subscales and in FACT-G and FACT-P total scores. FACT-P and FACT-P are instruments that assess quality of life in prostate cancer patients and in those with other chronic diseases.
Vitolins et al. J Clinical Oncology, 2013