Prostate Ca chemoprevention: Finasteride's role comes into focus

April 6, 2007

Mounting evidence suggests that finasteride (Proscar) can prevent the clinical manifestation of prostate cancer. Whether eligible men should receive the drug routinely must be an individualized decision, said Eric Klein, MD, of the Cleveland Clinic Lerner College of Medicine.

Mounting evidence suggests that finasteride (Proscar) can prevent the clinical manifestation of prostate cancer. Whether eligible men should receive the drug routinely must be an individualized decision, said Eric Klein, MD, of the Cleveland Clinic Lerner College of Medicine.

"Chemoprevention of prostate cancer is an attractive prospect," Dr. Klein told an early morning audience at the first Urology Congress, which opened yesterday in San Francisco.

"It is better to never be diagnosed with disease than to be diagnosed, followed by treatment with significant side effects. Results from the Prostate Cancer Prevention Trial [PCPT] show that finasteride reduces the risk of prostate cancer by 25%."

Early worries that finasteride may also increase the risk of high-grade prostate cancer are unfounded, Dr. Klein continued. While PCPT data showed a 25% increase in the incidence of high-grade tumors in the finasteride arm, more detailed analysis shows that the increase is actually an increase in diagnostic accuracy, not an increase in the incidence of disease.

Because the drug decreases the size of the gland by about 25%, biopsy needles are more likely to sample any tumors that are present.

"If you do the same number of biopsies in a smaller gland, it stands to reason that you will find more cancers," he explained. "The data support that conclusion."

Finasteride also increases the diagnostic accuracy of PSA, according to Dr. Klein. Simply putting a patient on finasteride should reduce PSA by about 50%, he explained. If there is no PSA drop after initiation of the drug, or if PSA shows any increase during therapy, the prostate should be biopsied.

The cost of finasteride remains an issue for many patients, Dr. Klein said, but the sexual side effects of the drug are highly overrated. Unpublished data show that sexual effects of the drug are minor and similar to age-related changes in sexual activity.

Chemoprevention of prostate cancer is an off-label use of finasteride, Dr. Klein noted. But for now, it remains the only chemopreventive agent with prospective data in prostate cancer. Retrospective trials suggest that statins reduce the incidence of prostate cancer by 51%, but there are no prospective data yet.

"Should finasteride be used as a preventive? You will all have to make up your own mind on this issue. There are benefits and costs here," Dr. Klein said.