The team also looked at tissue samples for a marker of benign disease -- called hyperplastic epithelial tissue -- and two markers associated with increased risk of prostate cancer -- the presence of precancerous lesions known as PIN (prostate intraepithelial neoplasia) and the rate of cell proliferation in the prostate gland. They found that, as expected, finasteride reduced the proportion of the hyperplastic epithelial tissue. But, the drug had no effect on PIN or proliferation, which are more strongly linked to the development of cancer.
The results suggest that though finasteride lowers DHT levels, the net effect of hormones acting on the prostate may be unchanged by the drug, according to Ross. That may be because of rising testosterone levels in the men taking finasteride. Although not as potent as DHT, testosterone can also spur prostate cell growth. "The biology is not as straightforward as many people have assumed," Ross concludes.
Notably, of the eight men who had precancerous lesions at the start of the study and were treated with finasteride, six developed cancer after one year. In comparison, in the no-treatment group, none of the five men with precancerous lesions got cancer. This finding, though in a small sub-group of the men, was statistically significant, leading researchers to write, "finasteride is unlikely to be useful and may even be harmful in men with PIN."
"If finasteride were to have had an anti-cancer effect, it is likely that it would have showed up in these patients," Ross says. The USC team holds off, however, on predicting the results of the national trial. "It is possible that the drug could have a beneficial effect in preventing prostate cancer in some men, though the results of this study suggest that this is unlikely," Ross says.
Richard J. Cote, Eila C. Skinner, Carol E. Salem, Susan J. Mertes, Frank Z.
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Contact: Eva Emerson or Brenda Maceo
eemerson@hsc.usc.edu
323-442-2830
University of Southern California
1-Aug-1998