Dietary supplements may promote prostate cancer progression

Hormonal components in over-the-counter dietary supplements may promote the progression of prostate cancer and decrease the effectiveness of anti-cancer drugs, report researchers at the University of Texas Southwestern Medical Center, Dallas. The findings, which appear in Clinical Cancer Research (2008; 14:607-11), reaffirm that patients should inform their doctors about any herbal or hormonal dietary supplements they are taking or are considering taking.

“Physicians need to ask their patients not only about the prescription drugs they may be taking, but-perhaps even more importantly-about the over-the-counter drugs and supplements, which may have a profound impact on certain health conditions,” said Claus Roehrborn, MD, a study co-author.

The researchers began their investigation when two patients being seen by UT Southwestern physicians developed aggressive prostate cancer within months of starting daily consumption of the same dietary supplement. Both men purchased the same product, one to develop stronger muscles and enhance sexual performance, the other to gain muscle.

Shahrokh Shariat, MD, the study’s lead author, worked with colleagues to analyze the supplement, which is not named in the study. The product’s label listed ingredients that were not present, misrepresented the concentrations of the ingredients present, and failed to list all the steroid hormones contained in the product.

Hormone analysis revealed that the supplement contained testosterone and estradiol. Researchers then tested the effect of the product on human prostate cancer cell lines. The product proved to be a more potent stimulator of cancer-cell growth than testosterone. Additionally, attempts to stop the cancer cell growth with increasing concentrations of the anti-cancer drug bicalutamide (Casodex) proved to be futile.

Based on the clinical data and cell culture experiments, the researchers filed an adverse event report with the FDA, which, in turn, issued a warning letter to the manufacturers, leading to the removal of the product from the market.