Activity of the Herbal Combination, PC-SPES, in Androgen-Independent (AI) Prostate Cancer (PC) Patients
K. Oh, Daniel J. George, Philip W. Kantoff,
INTRODUCTION -- Effective therapeutic options are limited for patients whose PC progresses after initial androgen ablation therapy. Estrogens have been shown to have secondary efficacy in AI PC. More recently, the herbal formulation PC-SPES was noted to have unique estrogenic activity.
METHODS -- 23 patients received PC-SPES (6 tablets daily) from February to November, 1999. Patients were eligible if they had progression of cancer after androgen ablation therapy. Prior secondary hormonal and chemotherapy was allowed. Patients received monthly PSA tests and examinations.
RESULTS -- Median age was 70 years old. Median duration of initial androgen ablation therapy was 16.5 months. 18 patients received prior secondary hormones (14-ketoconazole, 9-high-dose bicalutamide), while 10 received prior chemotherapy. Median follow-up was 3 mo (range 1-8 mo). At the start of therapy, median PSA was 84 ng/ml (mean 370). 20 of 23 patients (87%) experienced a post-therapy decline in PSA. The median decline in PSA in twenty responders was 55% (range 1-88%). 8/23 patients (35%) experienced a 1-50% decline in PSA, while 12/23 (52%) had a > 50% decline in PSA after PC-SPES. Median duration of response among all responders was only 2.25 mo (range 1-7 mo). One patient died from progressive prostate cancer. Of 13 patients with symptoms at the start of therapy, five noted some improvement, including decreased bone pain. Toxicity was mild, including nipple tenderness in 9 patients, fatigue and nausea in one patient each. One patient with a history of CAD developed angina after one month, controlled with medications. Of note, another patient who progressed after 12 years on DES and 6 mo on estramustine-based chemotherapy, subsequently responded to PC-SPES with a PSA decline from 219 to 84 ng/ml.
CONCLUSIONS -- In this preliminary study, PC-SPES appears to have activity in AI PC. The majority of patients demonstrated PSA declines, though duration of response was brief. Although PC-SPES has estrogenic effects, further studies are required to determine its mechanism of activity and role in treatment of AI PC.