Genistein supplement in prostate cancer trial
derived from soybeans and shiitake mushrooms, could help slow or
even halt the progression of early prostate cancer.
The new trial, to be carried out by a team at the University of California Davis Cancer Center, will test the action of genistein concentrated polysaccharide, or GCP, on men who are on active surveillance or 'watchful waiting' for prostate cancer.
Watchful waiting is recommended for some prostate cancers that cause no symptoms, are expected to grow very slowly, and are small and contained within one area of the prostate.
The new study builds on a preliminary trial, completed last year, that found GCP reduced levels of prostate-specific antigen (PSA) in a small group of 'watchful waiting' patients. Rising blood levels of PSA, a marker for prostate cancer, in men with diagnosed prostate cancer can be a signal of disease progression, while falling levels can signal remission.
GCP is already used as a complementary therapy for prostate cancer in Japan, Korea and other parts of Asia.
"If we can find a chemopreventive agent capable of slowing or stopping the progression of early, localised prostate cancer, we'll have something to offer men besides watchful waiting," said Ralph deVere White, professor and chair of urology at UC Davis School of Medicine and Medical Center and a principal investigator of the GCP trial.
"It would be an important development in prostate cancer," he added.
The preliminary trial of GCP in men with prostate cancer last year, published in the February issue of the journal Urology and previously reported at the May 2003 meeting of the American Urological Association, found that PSA levels stabilised or dropped in eight of 13 'watchful waiting' patients who took the supplement.
However, GCP did not improve PSA levels in study subjects who had received surgery, radiation or hormone therapy for their cancers, perhaps because their disease was more advanced or aggressive, or because the medical treatments reduced GCP concentrations within the prostate.
Recent research has also found another substance in soy, a group of molecules known as sphingolipids, to fight the development of tumours in the colon.
A study by the Fox Chase Cancer Center in the US found that more than half of men they surveyed were taking one or more supplements to prevent prostate cancer.
The new study is sponsored by GCP manufacturer Amino Up Chemical, based in Sapporo, Japan.
