Clinical and biologic activity of an estrogenic herbal combination (PC-SPES) in prostate cancer

N Engl J Med. 1998 Sep 17;339(12):785-91. doi: 10.1056/NEJM199809173391201.


Background: Herbal mixtures are popular alternatives to demonstrated therapies. PC-SPES, a commercially available combination of eight herbs, is used as a nonestrogenic treatment for cancer of the prostate. Since other herbal medicines have estrogenic effects in vitro, we tested the estrogenic activity of PC-SPES in yeast and mice and in men with prostate cancer.

Methods: We measured the estrogenic activity of PC-SPES with transcriptional-activation assays in yeast and a biologic assay in mice. We assessed the clinical activity of PC-SPES in eight patients with hormone-sensitive prostate cancer by measuring serum prostate-specific antigen and testosterone concentrations during and after treatment.

Results: 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 of six men with prostate cancer, PC-SPES decreased serum testosterone concentrations (P<0.05), and in eight of eight patients it decreased serum concentrations of prostate-specific antigen. All eight patients had breast tenderness and loss of libido, and one had venous thrombosis. High-performance liquid chromatography, gas chromatography, and mass spectrometry showed that PC-SPES contains estrogenic organic compounds that are distinct from diethylstilbestrol, estrone, and estradiol.

Conclusions: PC-SPES has potent estrogenic activity. The use of this unregulated mixture of herbs may confound the results of standard or experimental therapies and may produce clinically significant adverse effects.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Antineoplastic Agents, Phytogenic / adverse effects
  • Antineoplastic Agents, Phytogenic / chemistry
  • Antineoplastic Agents, Phytogenic / pharmacology*
  • Breast / drug effects
  • Drugs, Chinese Herbal / adverse effects
  • Drugs, Chinese Herbal / chemistry
  • Drugs, Chinese Herbal / pharmacology*
  • Female
  • Humans
  • Libido / drug effects
  • Male
  • Mice
  • Plant Extracts / adverse effects
  • Plant Extracts / chemistry
  • Plant Extracts / pharmacology*
  • Prostate-Specific Antigen / blood
  • Prostatic Neoplasms / drug therapy*
  • Prostatic Neoplasms / physiopathology
  • Receptors, Estrogen / drug effects*
  • Saccharomyces cerevisiae / drug effects
  • Testosterone / blood
  • Thrombophlebitis / chemically induced
  • Uterus / drug effects
  • Yeasts / drug effects


  • Antineoplastic Agents, Phytogenic
  • Drugs, Chinese Herbal
  • Plant Extracts
  • Receptors, Estrogen
  • herbal preparation PC-SPES
  • Testosterone
  • Prostate-Specific Antigen