Westport,CT (Reuters Health) Nov 20-PC-SPES, a mixture of extracts from eight different herbs, is effective in many patients with advanced prostate cancer, according to phase II study results reported in the November 1st Journal of Clinical Oncology.
Dr. Eric J. Small, from the University of California at San Fransisco, and colleaguestested the safety and effectiveness of PC-SPES in 33 men with androgen-dependent prostate cancer and 37 men with androgen-independent prostate cancer who had evidence of disease progression.
In the androgen-dependent cancer group, PC-SPES lowered the median PSA level from 7.9 ng/mL to undetectable levels in 26 (81.3%) patients, and all men in this group experienced declines of at least 80%, the report indicates. The PSA nadir was reached after a median 23 weeks and, as late as 74 weeks after treatment, no patient had shown evidence of progression.
Similarly, PC-SPES treatment of men with androgen-independent disease resulted in PSA declines of more than 50% (from a baseline median of 60.7 ng/mL) in 54% of patients, the authors report. The PSA nadir was reached after a median 10 weeks, and the median time to progression among responders was 18 weeks.
Endocrine side effects were common in both groups, with testosterone levels consistently falling below 50 ng/mL, the results indicate. This was reflected clinically in complete or or near-complete loss of libido, inability to have an erection, hot flushes, and breast tenderness and/or enlargement in most or all patients.
In general, however, treatment was well tolerated, according to the report. Other common side effects included leg cramps, diarrhea, and nausea. Three men developed pulmonary emboli requiring discontinuation of treatment.
"PC-SPES seems to have activity in the treatment of both androgen-dependent and androgen-independent prostate cancer and has acceptable toxicity," the authors conclude. "Further study is required to determine whether its effects exceed those expected with estrogen therapy."
How Pc-SPES works remains something of a mystery. "There may exist literally hundreds of unique compounds in an herbal mixture such as PC-SPES," the investigators write, "making it difficult to identify the active agent(s) and impossible to assure inter- and intralot variability."