When it was first introduced several years ago, it was looked upon askance by most of the medical community. However, clinical trials have demonstrated its benefits, specifically in patients who are experiencing a relapse after receiving traditional hormone or androgen deprivation therapy. Significant decreases in PSA have been observed with PC-SPES therapy. The exact mechanism of PC-SPES action is unknown. Part of the beneficial effect and perhaps the most important component of the beneficial effect of PC-SPES is its estrogenic activity.
Estrogens have a direct toxic effect on prostate cancer.
Therefore, the explanation of further activity of PC-SPES even in men who have been treated with other means of androgen deprivation and who have a castrate testosterone level might be the additional direct toxic effect of estrogen on the cancer cell. A number of studies are ongoing to clarify the specific mechanisms of PC-SPES and to explore its use in combination with other therapies. With regard to the latter, it is often learned that a patient is taking PC-SPES through casual conversation. Obviously if it is being taken and other therapies are employed it is difficult to separate the effect of one from the other. Therefore, patients, if they are taking PC-SPES, should be certain that their physicians are aware.