The Effect of High-dose Silybin-phytosome in Men With Prostate Cancer

A Pilot Biomarker Study of Oral Silybin-Phytosome Followed by Prostatectomy in Patients With Localized Prostate Cancer

Silibinin has demonstrated anti-cancer activity in the laboratory for several different cancer types, including prostate cancer. Silibinin was originally obtained from milk thistle. Silybin-Phytosome, an oral form of silibinin, has been tested previously in prostate cancer patients to determine the safety of high-dose treatment. This study is for men with prostate cancer who are planning to have their prostate surgically removed. Participants will be given Silybin-Phytosome three times a day from enrollment in the study until the time of their surgery. Participation in this study will not affect the timing of surgery. We obtain blood and urine samples at the start and completion of the trial in addition to prostate tissue from the surgery. These samples will be analyzed for the effect of Silybin-Phytosome at the end of the study.

Prostate cancer is the most common invasive malignancy and the second leading cause of cancer death in American males. In 2005, an estimated 230,000 men will be diagnosed and 30,000 will die from prostate cancer. The current estimated risk of developing prostate cancer is 1 in 6 men. Carcinogenesis and neoplastic progression of prostate cancer depend on both genetic and epigenetic factors; a multi-step process leads to progression from an androgen-dependent, non-metastatic phenotype to a more malignant, metastatic, androgen-independent phenotype. Treatment options for localized prostate cancer include watchful waiting, surgical prostatectomy, or targeted irradiation. The latter two treatments can cure cancers that are confined to the prostate gland, yet many patients have occult metastasis at the time of presentation, particularly to the bone or regional lymph nodes. Advanced prostate cancer with metastases presents a difficult therapeutic problem. Those who have disease progression with hormonal therapy have limited options. Patients initially treated with the combination of a Luteinizing Hormone Releasing Hormone (LHRH) analog and a synthetic antiandrogen occasionally respond to withdrawal of the anti-androgen. Chemotherapy is also an option in this setting, with docetaxel-based therapy having a small survival advantage in patients with hormone refractory prostate cancer. There is clearly a need for more effective regimens for patients with prostate cancer. With the current limitation in treatment options, there has been a renewed public and scientific interest in the use of less toxic herbal preparations in the treatment of cancer. Herbal supplements may play an especially important role in prostate cancer, considering its high incidence and oftentimes slow progression. However, before physicians can confidently recommend dietary supplementation, further scientific investigation is required.

Subjects in this group will take Silibin-Phytosome 13 grams daily, in three divided doses for 2-10 weeks.

Subjects will take Silibin-Phytosome for 2-10 weeks. The dose of Silibin-Phytosome is 13 grams daily, in three divided doses. Patients will be asked to mix 1 level teaspoon and 1 heaping ¼ teaspoon of Silybin-Phytosome powder into 6 tablespoons of applesauce for each dose.

To determine if measurable silibinin tissue levels are detectable in the prostate glands of men treated with Silybin-Phytosome administered according to the protocol. Analysis of silibinin in human fluid and tissue samples was carried out by Liquid chromatography - mass spectrometric (LC/MS/MS) following liquid extraction. Briefly, sample was extracted in acidified ethyl acetate by vortex. Following centrifugation, the organic layer was evaporated to dryness in a rotary evaporator and the samples were dissolved in acetonitrile/ammonium acetate with acetic acid for analysis. Sample analysis was done using an Applied Biosystems 3200 Q-Trap 1 triple quadrupole mass spectrometer with an Agilent 1100 Liquid Chromatography system and HTC-PAL Leap Autosampler. Quantitation of silibinin in samples was done by internal standard reference and batch analysis verified by the inclusion of spiked quality control samples in the appropriate matrix.

Inclusion Criteria: Patients must sign an Institutional Review Board (IRB) approved informed consent Age greater than 18 years old Male patients with histologically documented adenocarcinoma of the prostate Life expectancy greater than three months Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 Adequate organ function including a total Bilirubin less than or equal to 1.5 mg/dl Planned prostatectomy as treatment for prostate cancer. No known metastatic disease Exclusion Criteria: Prior definitive treatment for prostate cancer with surgery or radiation therapy Use of an investigational medication or device within one month of initiating study therapy. Prior systemic chemotherapy for prostate cancer or any hormonal therapy for prostate cancer. Any use of hormonal therapy (i.e. luteinizing hormone-releasing hormone analog) or anti-androgen therapy. Any condition or any medication which may interfere with the conduct of the study as determined by the principal investigator.

Flaig TW, Gustafson DL, Su LJ, Zirrolli JA, Crighton F, Harrison GS, Pierson AS, Agarwal R, Glode LM. A phase I and pharmacokinetic study of silybin-phytosome in prostate cancer patients. Invest New Drugs. 2007 Apr;25(2):139-46. doi: 10.1007/s10637-006-9019-2. Epub 2006 Nov 1.

Flaig TW, Glode M, Gustafson D, van Bokhoven A, Tao Y, Wilson S, Su LJ, Li Y, Harrison G, Agarwal R, Crawford ED, Lucia MS, Pollak M. A study of high-dose oral silybin-phytosome followed by prostatectomy in patients with localized prostate cancer. Prostate. 2010 Jun 1;70(8):848-55. doi: 10.1002/pros.21118.