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Human/Clinical Studies

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.[1]

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.

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.[2]

In a prospective clinical trial of 16 men with stage D3 metastatic prostate cancer in which all patients had failed therapy and had disease progression, the effects of PC-SPES on pain, quality of life, and side effects were assessed. Previous therapy was either orchidectomy or a luteinizing hormone–releasing agonist with or without antiandrogen. Hormonal therapy was continued throughout the trial to avoid the known withdrawal effect of antiandrogen on PSA levels. There was a significant decrease in pain scores such that the 14 patients on analgesics required an average of 40% less analgesics while taking PC-SPES. PC-SPES treatment was associated with improved function and emotional and physical well-being. PSA levels declined significantly after PC-SPES therapy (>50%). Side effects were breast tenderness, deep venous thrombosis, and mild dyspepsia.[3,4]

In a study of 70 patients, 37 with androgen -dependent (AD) disease and 33 with AI disease, the AD cohort was treated with PC-SPES only after an initial treatment with prostatectomy, radiation, cryotherapy, and/or hormonal therapy. Median duration of PSA response was greater than 57 weeks. All patients in the AD cohort had PSA declines within a range of 80% to 100%, and two patients with bone metastases showed improvement on radiographic analysis. Within the AI cohort, 54% (19 of 35) had a PSA decrease of greater than 50%, with median time to nadir of 10 weeks and a median duration of 18 weeks. Eight of the 16 patients who had received ketoconazole therapy prior to PC-SPES also obtained a decrease of greater than 50% in their PSA values. Testosterone levels within the AD group decreased to castrate levels (<50 ng/mL) in 94% of patients (31 of 33), and libido (25 of 25) and potency (15 of 15) were lost in all patients who entered the study. Side effects were hot flashes, gynecomastia/gynecodynia, and thromboembolic effects in 3 of 70 patients. Although the results of this trial were promising for the treatment of both AI and AD prostate cancer, it is not possible to assess what was responsible for these effects. This trial used PC-SPES from one single lot, but the published study does not indicate the lot number. The research was completed before 2000. No attempt was made to assess the possible contamination of the product.[3,5]

A prospective clinical series assessed the ability of PC-SPES to lower serum PSA levels in 33 prostate cancer patients. The patients had either refused conventional therapy or had failed previous cryosurgery, radiation therapy, and/or hormonal therapy. No overt signs of disease progression were found in any of the patients. At 2 months, PSA levels had decreased by a mean of 52% in 27 of the 31 patients and had increased in two patients. Of the five patients who had hormone -refractory disease, all had decreased serum PSA levels.[3,6]

In a continuation of the previous study, a total of 69 patients with either AI or AD disease were separated into three study groups. Group one (n = 43) had undergone previous therapy, including hormonal; group two (n = 22) developed AI after treatment; and group three (n = 4) had not undergone previous therapy. The study assessed PC-SPES activity in suppressing PSA levels. Patients were given three capsules of PC-SPES 3 times per day. PSA levels and side effects were observed for 24 months.[7]

In group one, 82% of patients (32 of 39) had a decrease in PSA levels, with 20 patients having a decrease of greater than 50% at 2 months’ follow-up; the decrease lasted for 24 months in two patients. In group two (AI patients), 90% (19 of 21) had a decrease in PSA at their 2-month follow-up, with 66% (14 of 21) having a decrease of greater than 50% in PSA levels. At 24 months, two patients had a decrease of 20% to 50% in pretreatment PSA levels. In group three, 50% (2 of 4) had a decrease of greater than 50% in PSA levels at 2 months, and the remaining two patients had an increase at 2 and 6 months. Eighty-two percent of study patients had a decreased PSA level after 2 months of therapy. Side effects included nipple tenderness (42%), gynecomastia (8%), hot flashes, and deep venous thrombosis.[7] In both Germany and the United Kingdom, PC-SPES–like formulations have been studied. A phase I trial of PC-Spes2 in the United Kingdom encountered tolerability problems due to diarrhea.[8]


  1. Oh WK, Kantoff PW, Weinberg V, et al.: Prospective, multicenter, randomized phase II trial of the herbal supplement, PC-SPES, and diethylstilbestrol in patients with androgen-independent prostate cancer. J Clin Oncol 22 (18): 3705-12, 2004. [PUBMED Abstract]
  2. Oh WK, George DJ, Hackmann K, et al.: Activity of the herbal combination, PC-SPES, in the treatment of patients with androgen-independent prostate cancer. Urology 57 (1): 122-6, 2001. [PUBMED Abstract]
  3. Pirani JF: The effects of phytotherapeutic agents on prostate cancer: an overview of recent clinical trials of PC SPES. Urology 58 (2 Suppl 1): 36-8, 2001. [PUBMED Abstract]
  4. Pfeifer BL, Pirani JF, Hamann SR, et al.: PC-SPES, a dietary supplement for the treatment of hormone-refractory prostate cancer. BJU Int 85 (4): 481-5, 2000. [PUBMED Abstract]
  5. Small EJ, Frohlich MW, Bok R, et al.: Prospective trial of the herbal supplement PC-SPES in patients with progressive prostate cancer. J Clin Oncol 18 (21): 3595-603, 2000. [PUBMED Abstract]
  6. de la Taille A, Hayek OR, Buttyan R, et al.: Effects of a phytotherapeutic agent, PC-SPES, on prostate cancer: a preliminary investigation on human cell lines and patients. BJU Int 84 (7): 845-50, 1999. [PUBMED Abstract]
  7. de la Taille A, Buttyan R, Hayek O, et al.: Herbal therapy PC-SPES: in vitro effects and evaluation of its efficacy in 69 patients with prostate cancer. J Urol 164 (4): 1229-34, 2000. [PUBMED Abstract]
  8. Shabbir M, Love J, Montgomery B: Phase I trial of PC-Spes2 in advanced hormone refractory prostate cancer. Oncol Rep 19 (3): 831-5, 2008. [PUBMED Abstract]
  • Updated: January 7, 2015