Herbs Lower PSA Level in Men with Advanced Prostate Cancer

October 27, 2000
News Office: Leslie Harris (415) 885-7277

A Chinese herbal supplement significantly reduced prostate specific antigen (PSA) levels - a protein in the blood often indicating prostate cancer - in men with advanced disease, according to a study by doctors at UCSF Medical Center. Doctors also found that some tumors shrank after men took the popular supplement, consisting of extracts from eight different herbs.

The study, published Nov. 1 in the Journal of Clinical Oncology, is one of the first to subject the herb PC-SPES to rigorous scientific scrutiny. The herbal supplement's name is derived from an acronym and Latin word -- "PC" stands for prostate cancer and "SPES" is Latin for hope.

Dr. Eric Small, an oncologist at UCSF Medical Center and lead author of the study, said, "We wanted to study PC-SPES and hold it to the same standard as we would any other new drug. This is the first attempt to study this herb in a scientifically methodical way."

The study evaluated 70 men divided into two groups: those with hormone dependent disease (33 patients) and those with hormone independent disease (37 patients).

Hormone-dependent prostate cancer is affected by the male sex hormone testosterone, which fuels prostate cancer growth. Tumors shrink or slow their growth as testosterone levels are reduced. As a result, PSA levels fall. Testosterone levels can be reduced by hormone medications, such as the female hormone estrogen, but tumors can become resistant to hormonal therapy.

Hormone-independent prostate cancer continues to progress despite low testosterone levels.

All of the men in the hormone-dependent group of the study had a PSA decline of greater than 80 percent, with a median period of that decline lasting 57 or more weeks. Only one patient had disease progression while taking the herbal supplement. About 97 percent of these patients had steep declines in their testosterone also, causing researchers to theorize PC-SPES may work like standard hormonal therapy, Small said. "We think PC-SPES is estrogen-like," he said.

In the men with hormone-independent disease, 19 men, or about 50 percent, had PSA declines of greater than 50 percent. Median time before PSA increased was 16 weeks. But several men in this group have not had any disease progression in more than a year of taking the herb.

The finding that PC-SPES can lower PSA levels in men with hormone independent disease is significant, Small said, because it represents another line of defense for patients when standard hormonal therapy fails to slow the disease.

Some men in both groups saw shrinkage of their tumors. Side effects included impotency, lowered sex drive and breast tenderness. Overall, PC-SPES was well tolerated. The men were enrolled in the trial for two years and were given a dose of nine capsules daily.

"In this group of patients we can use another hormone, but beyond that, short of chemotherapy, there is not much more we can do," Small said. "PC-SPES can be used as a second or third line hormone. We don't know what kind of impact it will have on survival, but it clearly offers a clinical benefit. It provides us with another treatment we can use before chemotherapy."

While PC-SPES appears to mimic estrogen in men with hormone-dependent disease, Small and his colleagues believe there may be other active anti-cancer ingredients in the supplement because it lowered PSA levels in men with hormone-independent disease whose testosterone was already low. "We have proven that this has some activity," Small said. "The next step is to sort out if this is any different from estrogen," he said.

Small and colleagues at Dana Farber Cancer Institute in Boston, Mass., are enrolling 100 men with hormone independent disease for a trial to test which agent -- estrogen or PC-SPES -- works better to slow the disease. Patients will be enrolled for a year. "The importance of that study is it will help us get to the mechanism of PC-SPES," Small said.

Other authors on the paper include Dr. Mark Frohlich, UCSF assistant professor of medicine; Dr. Robert Bok, UCSF assistant clinical professor of medicine; Dr. Katsuto Shinohara, UCSF assistant professor of urology; Dr. Gary Grossfeld, UCSF assistant professor of urology; Zinovi Rozenblat, UCSF clinical research associate; William Kevin Kelly, Memorial Sloan-Kettering Cancer Center; Michele Corry, UCSF; Dr. David Reese, UCSF assistant clinical professor of medicine. The study was supported by the Association for the Cure of Cancer of the Prostate (CaP CURE).

Prostate cancer is the most common cancer, excluding nonmelanoma skin cancers, in American men, according to the American Cancer Society. The organization estimates that 180,400 new cases of prostate cancer will be diagnosed in the United States this year. Prostate cancer is the second leading cause of cancer death in men, exceeded only by lung cancer. About 31,900 men in the United States will die of this disease during 2000, according to the American Cancer Society.