Effects of PC-SPES, an Herbal Compound, in Patients with Androgen Dependent Prostate Cancer

Eric J. Small, Michele Corry, Mark A. Frohlich, Robert A. Bok, Katsuto Shinohara,
William F. Kelly, David M. Reese, Univ of CA, San Francisco, CA;
Memorial Sloan-Kettering, New York, NY.

INTRODUCTION -- PC-SPES, a nutritional supplement consisting of 8 different herbs used for the treatment of prostate cancer, has been shown to have estrogenic activity, although other mechanisms of activity have been reported.

METHODS -- We studied the efficacy and toxicity of PC-SPES in two cohorts of prostate cancer patients demonstrating disease progression: a) hormone naive patients with normal testosterone levels (the basis of this report), and b) androgen independent patients. Thirty-three patients with hormone naïve prostate cancer were treated. Patients received 9 capsules a day of PC-SPES. Median follow-up is 50 weeks. Median PSA was 7.9 (0.9-81). Thirteen patients had untreated localized disease, 12 had local recurrence, 5 PSA only recurrence, and 2 untreated bone metastases.

RESULTS -- PSA fell by more than 80% in 100% of patients, and to undetectable in 21/33 (64%). The median duration of PSA decline was 46.5 weeks+, and no patient has come off therapy because of disease progression. 14/19 patients (74%) who had disease assessable by TRUS had significant (greater than 50%) decrease in tumor volume. Of 2 patients with positive bone scans, 1 improved and 1 was stable. Testosterone levels declined to < 50ng/ml in 31/33 (94%). 25/25 patients with libido present at study entry lost libido with therapy, and 15/15 patients who were potent at study entry lost potency. Gynecomastia/gynecodymia was observed in 100% of patients. 2/33 patients (6%) experienced a deep vein thrombosis. Grade1,2 diarrhea was seen in 33%, and leg cramps in 64%. Five patients have come off therapy (2 for DVT, 1 for breast tenderness, 1 for leg cramps, and 1 to pursue definitive local therapy).

CONCLUSIONS -- PC-SPES is able to produce ongoing lasting PSA declines in virtually all patients with hormone naive prostate cancer. In some patients a decline in PSA correlates with objective measures of tumor response. Testosterone declines and side effect profile suggest that the mechanism of action is estrogenic in nature.