Drug Offers Promise in Fight Against Prostate Cancer, But Also Raises Questions
Although treatments for prostate cancer are available, they frequently do more harm than good. Surgical removal of the prostate gland (
Methods to lower prostate cancer risk, therefore, are urgently needed. Since male sex hormones (androgens like testosterone) normally stimulate prostate cells to grow, researchers would like to know whether reducing the prostate’s exposure to androgens would lower the risk of prostate cancer.
Results from the Prostate Cancer Prevention Trial (PCPT)—the first major trial of chemoprevention for prostate cancer—published in the July 17, 2003 issue of
The New England Journal of Medicine
, indicate that the drug
, which is used to treat
About the Study
Between January 1994 and May 1997, researchers randomly assigned 18,882 men 55 years of age or older with a low risk of prostate cancer to 5 milligrams per day (mg/d) of finasteride (which inhibits the conversion of testosterone to dihydrotestosterone, the primary androgen in the prostate) or placebo for seven years. Men were eligible if they had no clinical indication of prostate cancer.
Participants were carefully followed for signs of prostate cancer over the study period. They underwent annual
Those subjects who were still alive and had not received a diagnosis of prostate cancer at the end of the study were advised to have a
was detected in 18.4% of the men in the finasteride group and 24.4% of the men in the placebo group, amounting to a significant cancer risk reduction of 24.8% for men treated with the drug. However, subjects who had cancer in the finasteride group were slightly more likely to have a more aggressive form (according to the
The researchers noted that 36.8% of men in the finasteride group and 28.9% in the placebo group temporarily discontinued treatment at some time during the study for reasons other than death or diagnosis of prostate cancer. Side effects were reported in both groups:
Because the results were so striking and the study’s objectives were met (and the conclusions were unlikely to change), researchers ended the trial 15 months early.
How Does This Affect You?
The findings from this study suggest that finasteride may be able to prevent the growth of microscopic prostate cancer in its early stages by preventing the gland from responding to stimulation from testosterone. While this is encouraging, there are still many unanswered questions.
For one, the cancer detection rate was high in this study, suggesting that insignificant cancers (those that would never have caused harm) were more likely to be diagnosed in study subjects than in the general population. A more meaningful finding, thus, would be if finasteride not only reduced the risk of developing prostate cancer but also reduced the risk of dying from it, something this study did not address.
A second surprising finding was the increase in the rate of aggressive cancers in the finasteride group. One explanation is that the drug affects the appearance of prostate cancer cells, leading pathologists to conclude incorrectly that the tumor is a more aggressive type. Another possibility is that finasteride actually causes more aggressive tumors to develop—either by preventing only low-grade tumors, or by making the prostate gland more favorable to aggressive tumors.
Finally, there is the matter of side effects. The incidence of adverse effects on sexual function was higher with finasteride, but the group also had a lower incidence of urinary symptoms and complications compared to the placebo group.
As with most prevention strategies, there are trade-offs. On balance, however, finasteride does not appear to be an attractive option. Men will have to weigh their individual cancer risk against the potential for the acceleration of high-grade cancers and troublesome side effects. At this point, however, there is no compelling reason for men currently taking finasteride for
American Cancer Society
National Cancer Institute
Prostate Cancer Research Institute
Thompson IM, Goodman PJ, Tangen CM, et al. The Influence of Finasteride on the Development of Prostate Cancer. NEJM . 2003;349(3):213-22.
Scardino PT. The Prevention of Prostate Cancer(The Dilemma Continues. NEJM . 2003;349(3):295-97.
Last reviewed July 3, 2003 by
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