PC-SPES and prostate cancer

PC-SPES: A Brief Overview

PC-SPES is a botanically based dietary supplement that has been used by men following prostate cancer treatment to reduce prostate-specific antigen levels. It is a complex matrix comprising 8 herbs whose known chemistry and biology do not account for the observed clinical activity. Recent disclosures have forced the product to be withdrawn from the market. Aspects of previous scientific research on the product, including clinical information, are reviewed, and some suggestions are offered for the future scientific needs of this product. Some thoughts are also offered on what the recall of PC-SPES means for the future scientific directions of the dietary supplement industry.

PC-SPES: herbal formulation for prostate cancer

PC-SPES is a potent eight-herb formulation sold directly to consumers; it has promising efficacy in the treatment of prostate cancer (CaP). The product induces a castrate status in most, if not all, men, resulting in a 50% or greater prostate-specific antigen reduction in the great majority of men with androgen-dependent CaP and in more than one half of the men with androgen-independent CaP. The duration of response is not yet clear. The efficacy of PC-SPES appears to exceed that of androgen ablation alone, but is not necessarily separate from an estrogenic effect. Common side effects include gynecomastia, nipple tenderness, loss of libido, and impotency; uncommon side effects include a 4% incidence of thromboembolic phenomena, but also two reports of bleeding diatheses. The mechanisms of action may involve downregulation of the androgen receptor, induction of apoptosis by way of inhibition of the bcl-2 gene, and increased expression of p53. Two marker compounds in PC-SPES are baicalin and oridonin, both of which exhibit antiproliferative effects in CaP cell lines. Thousands of men are currently obtaining this nonprescription medicine, and physicians should ask patients specifically about its use. PC-SPES is of great interest in men with androgen-independent CaP, an area in which future research should be primarily directed.

Herbal supplement PC-Spes for prostate cancer

OBJECTIVE

To determine the efficacy and toxicity of the herbal supplement PC-Spes in prostate cancer patients.

METHODS

Literature search through MEDLINE (1966-October 2001), PubMed, and abstracts from the Annual Meeting of the American Society of Clinical Oncology (1995-2001).

RESULTS

PC-Spes was associated with biochemical and clinical response in some prostate cancer patients. The mechanisms of action of PC-Spes appeared to be related to its estrogenic activity.

CONCLUSIONS

PC-Spes is associated with some efficacy in prostate cancer patients. Due to the limited data available, it should not be used to replace standard androgen suppression therapy in androgen-dependent patients. PC-Spes may have a role for patients who have failed standard treatments for androgen-independent disease and have no history of thromboembolism or abnormal bleeding. PC-Spes has a toxicity profile similar to those of androgen suppression and estrogen therapy.