NOTE: The information in this summary is no longer being updated and is provided for reference purposes only.
This cancer information summary provides an overview of the use of PC-SPES as a treatment in people with cancer. The summary includes a brief history of PC-SPES research, the results of clinical trials, and possible adverse effects of PC-SPES. Included in this summary is a discussion of the contamination of PC-SPES and its withdrawal from avenues of distribution.
This summary contains the following key information:
Note: Separate PDQ summaries on Prostate Cancer, Nutrition, and Dietary Supplements and Prostate Cancer Treatment are also available.
PC-SPES is a patented herbal mixture that was sold as a dietary supplement and used as a complementary and alternative medicine (CAM) treatment for prostate cancer. It is a combination of the following eight herbs:
With the exception of saw palmetto, the herbs in PC-SPES have been used individually or in combination in Traditional Chinese Medicine (TCM) for a variety of health problems, including those of the prostate, for hundreds of years.  
PC-SPES is an herbal product that resulted from a collaboration between a chemist at the New York Medical College in Valhalla, New York, and a Chinese herbalist and doctor of TCM in China. Their idea was to combine TCM with the scientific techniques of Western laboratory research. In the United States, a series of in vitro and in vivo laboratory studies was started on the mixture of herbs used in TCM specially formulated to treat prostate problems. Researchers published the results of these studies, which showed promising anticancer activity from PC-SPES.         
Considerable research has been conducted on the anticancer properties of the eight individual botanicals in PC-SPES.
Baikal skullcap (Scutellaria baicalensis)—Chinese name huang qin—contains baicalin and wogonin, two active flavones. Baicalin converts to baicalein, which is another active flavone. In vitro, baicalin and baicalein inhibit cell growth of AD LNCaP and JCA-1 AI human prostate cancer cell lines,   as well as inducing apoptosis in human LNCaP cells.  Baicalin also shows antimutagenic and antioxidant activity in vitro as well as free radical scavenging ability.      
Licorice (Glycyrrhiza glabra or Glycyrrhiza uralensis)—Chinese name gan cao—contains the very active flavonoid licochalcone A, which has demonstrated in vitro estrogenic activity.  This botanical shows a broad range of anticancer activity in vitro. It enhances the cytotoxicity of commonly used anticancer drugs and induces apoptosis in MCF-7 human breast cancer and HL-60 promyelocytic leukemia cell lines.    
Reishi mushroom (Ganoderma lucidum [Curtis: fr.] Karst.)—Chinese name ling zhi— has been shown to aid in the recovery of leukocyte counts in irradiated mice in a dose-dependent manner. It contains the polysaccharide G009, which has demonstrated antioxidant behavior against HL-60 cells in vitro and dose-dependent inhibition of lipid peroxidation in rat brain cells in vitro.     
Isatis (Isatis indigotica)—Chinese name da qing ve—contains active agents in each part of the plant.  TCM has different names for the medicinals coming from the leaf, stem, and root and uses these plant products for different purposes. Indirubin, an active ingredient, and its analogs have demonstrated inhibition of cyclin-dependent kinases in human mammary carcinoma cell line MCF-7 in vitro. 
Ginseng (Panax ginseng or Panax pseudoginseng var. notoginseng)—Chinese name tianqi—contains ginsenosides and saponins. Of the 30 ginsenosides that have been isolated from Panax ginseng, only the 20(S)-protopanaxadiol type R3 has inhibited cell growth and suppressed PSA expression, androgen receptor and 5-alpha-reductase activity, and PCNA production in vitro.   
Chrysanthemum flowers (Dendranthema morifolium)—Chinese name ju hua—contain triterpene diols and triols. Arnidiol exhibited cytotoxicity in vitro against 58 of the 60 human cancer cell lines developed by the National Cancer Institute (NCI) Developmental Therapeutics Program. 
The botanical rabdosia rubescens (Isodon rubescens)—Chinese name dong ling cao—has two very active agents, oridonin and rubesencin b. Oridonin inhibits DNA synthesis in vitro,  and rubesencin b inhibited cell growth in cancer cell lines in vitro and in a mouse model. 
Saw palmetto (Serenoa repens) is the only botanical in PC-SPES that is not used in TCM. There is strong evidence from human trials that saw palmetto has some activity against benign prostatic hypertrophy (BPH), including improved urine flow and less erectile dysfunction when compared with placebo or finasteride. S. repens also exhibits antiestrogenic activity in placebo-controlled BPH trials. In LNCaP cells, S. repens produced apoptosis in vitro.     
Exactly how PC-SPES works in the body is still unknown. The presence of adulterants and varying amounts of the active agents in each lot of PC-SPES complicates the interpretation of any results from studies that might lead to an explanation of its mechanisms of action. More studies of the individual components of the mixture and testing of a standard formulation that is free of adulterants are needed before any conclusions can be reached about the level of cytotoxicity, antineoplasticity, or estrogenicity of PC-SPES.
The National Center for Complementary and Integrative Health (NCCIH) stopped funding to studies of PC-SPES after the drug contamination was detected and made public, although the laboratory studies were later resumed.
Although manufacturers are selling supplements purporting to be substitutes, the only company that had a license from the patent holder to manufacture PC-SPES is no longer in business, and the product cannot be legally manufactured in the United States without the patent holder’s permission. PC-SPES is not legally available in the United States.
In 1997, the herbal formula for PC-SPES was patented in the United States.  A company, BotanicLab (Brea, California), was formed to produce, distribute, and sell the product. PC-SPES was sold through the BotanicLab website (the website was taken down after PC-SPES was recalled) and through selected distributors. Anecdotal information about the product and its positive effects was widely circulated on the Internet through websites that informed prostate cancer patients about new developments in treatment. At the same time, the published papers were being read by the scientific community, and the findings were presented at various conferences. As a result, clinicians and researchers began looking at PC-SPES as one of the first viable treatments to come out of the alternative medicine community.
The manufacturing process for PC-SPES has been described by the manufacturer as follows: extracts of raw plant material were obtained from the specified plants, which were grown in particular geographic regions in China and harvested at certain times of the year to reduce the natural variation inherent in any biological product. The extracts were shipped to the United States, where high-performance liquid chromatography (HPLC) was used to monitor the key active compounds—which are believed to be directly related to the clinical effects—for batch-to-batch reproducibility. Activity-related biomarkers were kept in a constant concentration from lot to lot. A commercial testing laboratory (Truesdail Laboratory; Tustin, California) was used to guarantee that each batch was free from contamination with heavy metals, pesticides, microorganisms and products, and prescription drugs. Each lot was standardized by an anticancer bioassay for an effective dose of 50% in vitro inhibition of cell growth using human LNCaP cells for androgen-dependent (AD) prostate cancer and DU-145 cells for androgen-independent (AI) prostate cancer. The powder was then encapsulated, bottled, labeled, and sterilized at the BotanicLab facility. 
In 2001, allegations that PC-SPES contained the synthetic estrogen diethylstilbestrol (DES) started to appear on e-mail listservs used by prostate cancer patients and in online newsletters. Prostate cancer patients who were taking PC-SPES noticed that their recent medication was not as effective as the previous batches.  A sample of PC-SPES submitted to a testing laboratory by BotanicLab in August 2001 found no DES. BotanicLab posted the letter from the laboratory on their website, claiming that PC-SPES contained no DES. However, in other tests of six different lots of PC-SPES received from two different sources in August 2001, Rocky Mountain Instrumental Laboratory found varying amounts of DES in three lots. More tests done by the California Department of Health Services in February 2002 did not find DES but did find warfarin, a prescription drug used as a blood thinner. 
The presence of a synthetic estrogen such as DES was suspected early in the clinical use of PC-SPES after reports in the literature discussed the mixture’s estrogen-like ability to lower prostate-specific antigen (PSA) levels in AD prostate cancer patients. In addition, the side effects of treatment were similar to those of estrogen therapy.    In one study, patients who showed the most response to PC-SPES were also those who were the most responsive to DES.   The same study also attempted to find out whether DES or similar compounds were present in PC-SPES. Transcriptional activation assays in yeast strain PL3 Saccharomyces cerevisiae using an ethanolic extract of PC-SPES showed estrogenic activity similar to 1nM estradiol. In addition, ovariectomized CD-1 mice showed substantially increased uterine weights. HPLC, gas chromatography, and mass spectrometry did not reveal the presence of DES but rather that of a compound with similar chemical characteristics. The authors of the report concluded that PC-SPES contains estrogenic compounds that are distinct from DES or other synthetic estrogens. 
A definitive evaluation of PC-SPES analyzed specific lots of PC-SPES capsules manufactured from 1996 to 2001.  In addition to using HPLC to isolate, identify, and quantify the synthetic drugs and active phytoestrogens, this study also identified components using proton nuclear magnetic resonance, gas chromatography/mass spectrometry, and mass spectra analysis. Tests showed the presence of the synthetic drugs indomethacin (a nonsteroidal anti-inflammatory drug not previously reported in the literature or found in other testing), DES, and warfarin. Testing was also done for concentrations of the two naturally occurring phytosterols, licochalcone A and baicalin. Test results indicated a history of rising and falling levels of contamination by the three synthetic drugs and a recent rise in the naturally occurring phytochemicals in PC-SPES. Lots of PC-SPES manufactured in 1996 through mid-1999 contained indomethacin ranging from 1.07 mg/g to 13.19 mg/g and DES ranging from 107.28 µg/g to 159.27 µg/g and were 2 to 6 times more antineoplastic and up to 50 times more estrogenic than lots manufactured after the spring of 1999. In vitro testing of ethanolic extracts of PC-SPES against LNCaP, PC-3, and DU-145 prostate cancer cell lines showed a decrease in both antineoplasticity and estrogenicity in lots of PC-SPES manufactured in June 1998 through August 2001, which correlated with the amount of DES and indomethacin contamination.  Another in vitro test of suspected lots of PC-SPES manufactured from 2000 to 2001 also showed the presence of DES. 
Although the laboratory testing showed that certain lots of the mixture contained indomethacin, warfarin, and DES, the amount of DES present may not have accounted for all of the estrogenic effect of PC-SPES. There is some evidence that the mixture acts differently from DES at the molecular level.   In addition, its anticancer effects on both AI prostate cancer and AD prostate cancer may point to a mechanism other than estrogen-like activity.    The in vitro activity of PC-SPES against cancer cells other than prostate also gives rise to the speculation that its estrogen-like qualities might not account for all of the mixture’s anticancer activity.  
Before the discovery of diethylstilbestrol (DES), warfarin, and indomethacin contamination, PC-SPES appeared to have some efficacy as an antineoplastic agent in laboratory and animal studies. These studies are presented below. Due to the fact that there was no standardization of the composition of PC-SPES or any knowledge of the amount of contamination of each lot used in testing, it is difficult to interpret the data from these studies.
In one study that attempted to measure the effects of the whole PC-SPES mixture versus that of individual herbs of PC-SPES on prostate-specific antigen (PSA) expression and cell growth, LNCaP cells were treated with ethanol extracts of PC-SPES and each of the eight herbs. The PC-SPES mixture reduced cell growth by 72% to 80%, while Dendranthema morifolium (Ramat.) Tzvelev (synonym Chrysanthemum morifolium) (chrysanthemum) produced the highest reduction of the herb group at 85%. Panax pseudoginseng var. notoginseng Hoo & tseng (Synonym Panax notoginseng [Burkill] F.H.Chen) was next at 80.9% reduction, followed by Glycyrrhiza uralensis Fisch ex DC. (73%). The lowest reduction in cell growth was exhibited by Serenoa repens (Bartr.) Small (14.5%). Scutellaria baicalensis Georgi, Serenoa repens, and Glycyrrhiza uralensis lowered PSA expression, but each of the other herbs increased PSA expression. The ability of individual herbs to reduce PSA expression was not uniform, but the PC-SPES mixture as a whole exhibited a uniform response. The varying results with the individual herbs and the positive response of the cells (i.e., increased cytotoxicity and reduced PSA expression) to the aggregate PC-SPES mixture may suggest that the botanicals in PC-SPES work in concert and that no individual herb can account for the overall effects of the mixture. 
In other studies, PC-SPES was found to inhibit clonal growth in three human prostate cancer cell lines: LNCaP, PC-3, and DU-145. Cell cycle analysis showed cell cycle arrest at the G2 phase.  Cell proliferation and reduced clonogenicity were observed in cancer cell lines other than those of prostate cancer: human breast carcinoma lines MCF-7 and T47-D, SK-N-MC neuroepithelioma, COLO 38 melanoma, U937 histiomonocytic lymphoma, and HL-60 and MOLT-4 leukemias. Cytotoxic and cytostatic effects of PC-SPES were common to all tumor cell lines tested. 
In another study evaluating regulation of PSA expression and androgen receptor (AR) activity, LNCaP prostate cancer cell lines showed downregulation of both proliferating cell nuclear antigen (PCNA) and PSA expression. PSA changes occurred concurrently with the decrease of PCNA. The results suggest that PC-SPES modulates cell growth by changing PCNA expression and may decrease PSA levels indirectly by suppressing AR expression. 
None of the studies above indicated lot number or year of manufacture of the PC-SPES used. Therefore, it is not possible to assess the amount of contamination of the mixtures used in the studies or whether the mixtures used were not in fact contaminated.
A 1998 study that evaluated estrogenic activity of extracts of PC-SPES, ginseng (Panax ginseng C.A. Meyer), saw palmetto, DES, and estrone (estradiol-17 beta) in vitro reported on the estrogenic response of ovariectomized CD-1 mice to PC-SPES extract as well as the response to PC-SPES capsules in eight prostate cancer patients who had received previous therapy.  This study used four samples of PC-SPES ordered in separate purchases from BotanicLab. No lot numbers were supplied in the study. Lot numbers from October 1996 through July 1998 were later tested for contamination and had DES levels of 114.74 μg/g to 159.27 μg/g, as well as the highest detected levels of indomethacin of the PC-SPES lots tested.  In vitro tests of PC-SPES extract or estradiol showed estrogenic activity similar to 1 nM estradiol on estrogen receptor Y253 yeast strain. Transcriptional activation assays in yeast strain PL3 Saccharomyces cerevisiae with ethanolic extract of PC-SPES exhibited estrogen-like effects. In the eight prostate cancer patients, serum testosterone concentrations decreased during the use of PC-SPES and increased within 3 weeks after treatment was discontinued. PSA levels decreased in all eight patients. Side effects in all eight patients were similar to those seen after treatment with estrogen: breast tenderness and loss of libido. One patient had superficial venous thrombosis. In addition to baicalin, two other compounds purified from PC-SPES, isoliquiritigenin and wogonin, have been shown to reduce PSA levels and downregulate AR. 
By incorporating PC-SPES into the rat diet, researchers conducting an in vivo study showed antitumor effects using a Dunning R3327 rat prostate cancer model. Levels of 0.05% and 0.025% of dietary PC-SPES were fed to the rats over a 6-week period. No toxicity was seen, nor was there a difference in the food intake of the rats during this time. Pulmonary tumors were induced by intradermal injections of MAT-LyLu cells, which are particularly resistant to many forms of treatment. Tumor incidence was inhibited in a dose-dependent manner, and the rate of tumor growth showed the same dose-dependent response.  
In another study, which used male BNX nu/nu immunodeficient nude mice, PC-SPES was also administered orally, but in suspension. The mice received 300 rad of whole-body irradiation, after which they were inoculated with either PC-3 or DU-145 prostate cancer cell lines. Treatment with PC-SPES began the day after injection. Results showed that PC-SPES suppressed the growth of DU-145 tumors compared with tumor growth in the control group. Cytological analysis showed apoptosis in the treated group that was not apparent in the control group. 
In two other studies, clinical studies of patients were initiated along with in vitro and in vivo research. The results of these two patient groups are discussed in the Human/Clinical Trials section of this summary. The first study, preceding more extensive research, examined in vitro activity of PC-SPES against LNCaP, LNCaP-bcl-2, PC-3, and DU-145 cells lines. Results showed that PC-SPES was active in suppressing both hormone-sensitive and hormone-insensitive prostate cancer cell lines. In the subsequent study, research was conducted in vitro on the ability of PC-SPES to induce apoptosis in androgen-independent (AI) prostate cancer cell lines, and in vivo on the effect of oral PC-SPES on the growth of xenografted PC-3 tumors in immunodeficient male mice. Mice in the treatment arm—in which treatment was started 1 week after implantation—showed a significant decrease in tumor weight when compared with mice in the control arm. PC-SPES showed activity against both androgen-sensitive and AI prostate cancer in the patients and suppressed tumor growth in AI tumors in mice.    In both studies, the patients were given capsules manufactured between 1996 and 1999, a time when contamination levels of DES were highest. 
Another study in rats demonstrated that PC-SPES (one lot contaminated with DES and one lot without DES) caused some decrease in the activity of a liver enzyme involved in drug metabolism (CYP3A). 
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.
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. 
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.  
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.  
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.  
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. 
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.  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. 
Adverse effects of PC-SPES treatment were similar to those of hormonal drugs. The percentages indicate the approximate low-to-high range of side effects reported in the studies. It is difficult to compile accurate numbers from all studies reporting side effects because they are not consistently reported. Some studies concatenated categories of side effects, some did not report specific numbers or percentages, and some reported a few side effects while not reporting others. The following references indicate the studies from which the percentages come:
To assist readers in evaluating the results of human studies of integrative, alternative, and complementary therapies for cancer, the strength of the evidence (i.e., the levels of evidence) associated with each type of treatment is provided whenever possible. To qualify for a level of evidence analysis, a study must:
The lack of consistent composition of PC-SPES due to varying concentrations of adulterants makes it difficult to determine the effects of PC-SPES in humans; therefore, no level of evidence analysis is possible for this treatment. At this time, the use of PC-SPES as a treatment for cancer cannot be recommended outside the context of well-designed clinical trials.
For additional information about levels of evidence analysis, refer to Levels of Evidence for Human Studies of Integrative, Alternative, and Complementary Therapies.
The PDQ cancer information summaries are reviewed regularly and updated as new information becomes available. This section describes the latest changes made to this summary as of the date above.
Editorial changes were made to this summary.
This summary is written and maintained by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, which is editorially independent of NCI. The summary reflects an independent review of the literature and does not represent a policy statement of NCI or NIH. More information about summary policies and the role of the PDQ Editorial Boards in maintaining the PDQ summaries can be found on the About This PDQ Summary and PDQ® - NCI's Comprehensive Cancer Database pages.
This PDQ cancer information summary for health professionals provides comprehensive, peer-reviewed, evidence-based information about the use of PC-SPES in the treatment of people with cancer. It is intended as a resource to inform and assist clinicians who care for cancer patients. It does not provide formal guidelines or recommendations for making health care decisions.
This summary is reviewed regularly and updated as necessary by the PDQ Integrative, Alternative, and Complementary Therapies Editorial Board, which is editorially independent of the National Cancer Institute (NCI). The summary reflects an independent review of the literature and does not represent a policy statement of NCI or the National Institutes of Health (NIH).
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PDQ® Integrative, Alternative, and Complementary Therapies Editorial Board. PDQ PC-SPES. Bethesda, MD: National Cancer Institute. Updated <MM/DD/YYYY>. Available at: https://www.cancer.gov/about-cancer/treatment/cam/hp/pc-spes-pdq. Accessed <MM/DD/YYYY>. [PMID: 26389352]
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Date first published: 2004-11-22 Date last modified: 2017-07-27
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