Prostate Cancer Supplement Contaminated
PC-SPES Tainted With Synthetic Drugs
Sept. 4, 2002 -- An herbal dietary supplement that promised to give new hope to prostate cancer patients actually contained synthetic drugs that were likely responsible for its cancer-fighting benefits.
A chemical analysis of the supplement known as PC-SPES shows it was contaminated with the drugs Coumadin, Indocin (indomethacin), and diethylstilbestrol (DES). Coumadin is a blood thinner used to treat heart disease and prevent blood clots; Indocin is an anti-inflammatory for arthritis; and DES is a synthetic estrogen used years ago to prevent premature labor and miscarriage. DES has since been linked to health problems in the female children of women who'd taken the drug.
Both Indocin and DES are known to have cancer-fighting properties.
The herbal mixture was widely used to treat prostate cancer after early studies showed it to be effective at reducing the prostate cancer marker prostate-specific antigen (PSA), in men with the disease. But initial attempts to identify the active ingredients in PC-SPES were inconclusive.
The supplement, whose name combines the initials for prostate cancer and the Latin word for hope (spes), was first introduced in the U.S. in 1996. Its manufacturer says the supplement is a mixture of seven medicinal herbs plus saw palmetto.
But concerns grew that the supplement might contain other, synthetic drugs after men taking PC-SPES developed bleeding or blood-clotting problems. Those concerns eventually prompted the manufacturer, BotanicLab, to voluntarily recall the product earlier this year. The company subsequently went out of business.
In a study published in the Sept. 4 issue of the Journal of the National Cancer Institute, researchers analyzed eight lots of PC-SPES produced between 1996 and mid-2001. Their analysis showed that all lots contained Indocin and most contained DES. Lots produced after 1998 also contained varying amounts of Coumadin.
"The origin of the three potent synthetic drugs in PC-SPES is puzzling," says researcher Milos Sovak, MD, of the Biophysica Foundation in La Jolla, Calif.
Sovak and colleagues found that later lots containing less of the synthetic drugs showed as much as six times less anticancer potency than earlier lots containing higher concentrations of the drugs.
In an editorial accompanying the study, Jeffrey White, MD, of the National Cancer Institute, says these findings reveal the inherent problems of studying herbal dietary supplements -- the concentration of their active ingredients varies widely and they are easily contaminated.
White says the lessons of PC-SPES show that researchers should consider incorporating regular quality control evaluations by independent laboratories throughout their research on herbal supplements.