CLINICAL AND BIOLOGIC ACTIVITY OF AN ESTROGENIC HERBAL COMBINATION (PC-SPES) IN PROSTATE-CANCER

Background Herbal mixtures are popular alternatives to demonstrated th erapies. PC-SPES, a commercially available combination of eight herbs, is used as a nonestrogenic treatment for cancer of the prostate. Sinc e other herbal medicines have estrogenic effects in vitro, we tested t he estrogenic activity of PC-SPES in yeast and mice and in men with pr ostate cancer. Methods We measured the estrogenic activity of PC-SPES with transcriptional-activation assays in yeast and a biologic assay i n mice. We assessed the clinical activity of PC-SPES in eight patients with hormone-sensitive prostate cancer by measuring serum prostate-sp ecific antigen and testosterone concentrations during and after treatm ent. Results In complementary yeast assays, a 1:200 dilution of an eth anol extract of PC-SPES had estrogenic activity similar to that of 1 n M estradiol, and in ovariectomized CD-1 mice, the herbal mixture incre ased uterine weights substantially. In six of six men with prostate ca ncer, PC-SPES decreased serum testosterone concentrations (P<0.05), an d in eight of eight patients it decreased serum concentrations of pros tate-specific antigen. All eight patients had breast tenderness and lo ss of libido, and one had venous thrombosis. High-performance liquid c hromatography, gas chromatography, and mass spectrometry showed that P C-SPES contains estrogenic organic compounds that are distinct from di ethylstilbestrol, estrone, and estradiol. Conclusions PC-SPES has pote nt estrogenic activity. The use of this unregulated mixture of herbs m ay confound the results of standard or experimental therapies and may produce clinically significant adverse effects. (N Eng[ J Med 1998;339 :785-91.) (C) 1998, Massachusetts Medical Society.