PC-SPES is a combination of seven Chinese medicinal herbs [Reishi (Ganoderma lucidum) spores, Balkal skullcap (Scutellaria baicalenesis) root, Rabdosia (Rabdosia rubescens) root, Dyer's wood (Isatis indigotica) root, mum (Dendranthema morifolium) flower, san-qi ginseng (Panax notoginseng) bark and licorice (Glycyrrhiza glabra) root] with the addition of one North American herb, saw palmetto. This herbal product appeared a few years ago and is widely used by patients as a treatment for their prostate cancer. The story of this herbal product illustrates the positive and negative aspects of the current regulatory environment with regard to supplements. This product did not proceed through the standard process by which prescription drugs are approved by the FDA. Shortly after this product was introduced, many of us became aware that in some patients this product induced a significant decrease in tumor size. Physicians initially had no information about appropriate dosing, side effects and antitumor activity of this preparation.
Physicians specializing in prostate cancer have gathered experience with the use of this herbal product, largely because patients decided on their own to try it. Reports about PC-SPES then began to appear in medical literature. In one of the first clinical and experimental studies to evaluate the effect of PC-SPES in humans, DiPaola and associates61 tested the estrogenic activity of PC-SPES in yeast and mice, and in men with prostate cancer. In this study, they measured the estrogenic activity of PC-SPES with transcriptional-activation assays in yeast and a biologic assay in mice. The clinical activity of PC-SPES was evaluated in eight patients with hormone-sensitive prostate cancer by measuring serum prostate-specific antigen and testosterone concentrations during and after treatment. In complementary yeast assays, a 1:200 dilution of an ethanol extract of PC-SPES had estrogenic activity similar to that of 1 nM estradiol, and in ovariectomized CD-1 mice, the herbal mixture increased uterine weights substantially. In six out of six men with hormone-sensitive prostate cancer, PC-SPES decreased serum testosterone concentrations and in eight out of eight patients it decreased serum concentrations of PSA. All eight patients had breast tenderness and loss of libido, and one had venous thrombosis. High-performance liquid chromatography, gas chromatography and mass spec-trometry showed that PC-SPES contains estrogenic organic compounds that are distinct from diethylstilbestrol, estrone and estradiol.
This exciting study was followed by several other recent studies which examined both in vitro and clinical effects of PC-SPES. At UCSF,62 33 patients with androgen-dependent prostate cancer (ADPCa) and 37 patients with androgen-independent prostate cancer (AIPCa) were treated with PC-SPES (nine capsules daily). All ADPCa patients experienced a PSA decline of >80%, with a median duration of 57+ weeks. No patient developed PSA progression. Almost all of these patients had declines of testosterone to the anorchid range. Nineteen (54%) of 35 AIPCa patients had a PSA decline of >50%, a commonly used surrogate index for a robust response in these clinical situations.62 Median time to PSA progression was 4 months. Of 25 patients with positive bone scans, two had improvement, seven had stable disease, 11 had progressive disease and five did not have a repeat bone scan because of PSA progression. Severe toxicities included thrombo-embolic events and allergic reactions. Other frequent toxicities included gynecomastia/gynecodynia, leg cramps and grade 1 or 2 diarrhea.
The study at Columbia University evaluated 69 patients with prostate cancer treated with PC-SPES (three capsules daily).63 Serum PSA responses and side effects were evaluated. Of the patients with prostate cancer, 82% had decreased serum PSA 2 months, 78% 6 months and 88% 12 months after treatment with PC-SPES. Side effects in the treated patient population included nipple tenderness in 42% and phlebitis requiring heparinization in 2%. In a recent study from the Dana-Farber Cancer Institute, 23 patients with AIPCa were treated with PC-SPES (six capsules daily). With a median follow-up of 8 months, 20 patients experienced a post-therapy decline in PSA. Twelve patients (52%) had a >50% decline in PSA. The median duration of the PSA response was 2.5 months. Toxicity was mild and included nipple tenderness, nausea and diarrhea. In univariate analyses, older patients and those with a longer duration of initial androgen ablation therapy were more likely to respond to PC-SPES.64
In recent in vitro studies from Columbia University,63 PC-SPES was evaluated for its ability to induce apoptosis on human prostate cancer cell lines LNCaP (hormone sensitive), PC3 (hormone independent) and DU145 (hormone independent). The effect of oral PC-SPES on growth of PC3 tumors present in male immunodeficient mice was studied. All of the cultured prostate cancer cell lines had a significant dose-dependent induction of apoptosis following exposure to PC-SPES. Immunodeficient mice xenografted with the PC3 cell line had reduced tumor volume compared with sham-treated controls when they were treated with a PC-SPES extract from the time of tumor cell implantation but not when the treatment was begun 1 week after tumor cell implantation.
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