One published randomized cross-over study of patients with androgen-independent (AI) prostate cancer who initially received either 960 mg of PC-SPES 3 times a day or 3 mg of diethylstilbestrol (DES) once a day before crossing over to the other regimen; when disease progression occurred, there were reports of data demonstrating the presence and levels of adulterants in the four lots of PC-SPES used in this trial. The lots were manufactured by BotanicLab (Brea, California). The study was halted and chemical analyses of the lots were performed. The analyses showed that all four lots of PC-SPES contained amounts of DES ranging from 0.1 μg/g to 32.7μg/g, and that one lot contained varying amounts of ethinyl estradiol. The authors concluded that the presence of these adulterants rendered their results inconclusive.
Several nonrandomized clinical studies published between 1999 and 2003 described the results of clinical trials conducted before adulterants had been conclusively identified in PC-SPES lots and before it was known that there was significant variation in naturally occurring active agents, such as baicalein and licochalcone-A, in the lots. These studies, many of which enrolled small numbers of patients, did not identify the source of the lots that were used in the trials, nor did they identify where patients acquired PC-SPES.
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In addition to the confounding effects of adulterants on the clinical trial results discussed below, the fact that an optimal dose of PC-SPES remains undetermined and that dose varies among these studies makes it difficult to compare their findings.
In a retrospective study of 23 consecutive patients with AI disease, charts were evaluated for patients' responses to PC-SPES and the occurrence of any toxicity. There is no report of where the patients acquired their PC-SPES or what lots were used. Patients were all seen between February and November in 1999. Patients ranged in age from 51 to 88 years, with a median age of 70 years. All had previous initial androgen ablation for a period of 6 months to 144 months. Ten patients had received chemotherapy, 13 had not. More than half of the patients with AI showed a post-therapy prostate-specific antigen (PSA) decline of 50% or greater. Median time to PSA progression was 6 months. The side effects were similar to those of estrogen therapy (gynecomastia and impotence). Other side effects were nausea/vomiting and diarrhea and to a lesser extent, allergic reactions, leg cramps, and leg swelling.