This complementary and alternative medicine (CAM) information summary provides an overview of the use of PC-SPES as a treatment for cancer. The summary includes a brief history of PC-SPES research, the results of clinical trials, and possible adverse effects of PC-SPES. Included in this summary is a discussion of the contamination of PC-SPES and its withdrawal from avenues of distribution.

This summary contains the following key information:

• PC-SPES is a patented mixture of eight herbs.
• PC-SPES was sold as a dietary supplement to support and promote healthy prostate function.
• Each herb used in PC-SPES has been reported to have anti-inflammatory, antioxidant, or anticarcinogenic properties.
• PC-SPES was recalled and withdrawn from the market because certain batches were contaminated with Food and Drug Administration–controlled prescription drugs.
• The manufacturer is no longer in operation, and PC-SPES is no longer being made.
• There is evidence from both laboratory and animal studies to suggest that PC-SPES had some effect in inhibiting prostate cancer cell growth and prostate-specific antigen (PSA) expression, but it is not known whether these results were caused by contaminants such as diethylstilbestrol (DES), which is an estrogenic compound, the herbs in PC-SPES, or their combination.
• Evidence from clinical trials has shown that PC-SPES lowers PSA and testosterone levels in humans, but it is not known whether these results were caused by contaminants, the herbs in PC-SPES, or their combination.
• There is some evidence to suggest that PC-SPES has some anticancer effects that are not related to estrogen-like activity.
• Although there are products that claim to be substitutes for PC-SPES, they are not the patented original formulation. Few of these products have been the subject of laboratory or clinical trials reported in the peer-reviewed medical literature.

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