New findings from a Finnish study confirm previous research that finasteride use is associated with a decreased risk of prostate cancer.

In a study of participants in the Finnish Prostate Cancer Screening Trial, investigators evaluated prostate cancer incidence by stage and grade as well as by serum PSA values among men who used finasteride, a 5α-reductase inhibitor, or an alpha blocker as treatment for benign prostatic hyperplasia (BPH). The men were screened at four-year intervals. During 1996-2004, 23,320 men participated in at least one of the three screening rounds.

Of the 23,320 men, 1,754 men (7.5%) had used finasteride and 3,848 (16.5%) had used an alpha blocker (either tamsulosin or alfuzosin). Compared with nonusers of these medications, screen-positive finasteride users (those with a PSA level of 4 ng/mL or higher) had an overall decrease in prostate cancer incidence that translated into a 38% decreased risk of the malignancy.

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This effect primarily was driven by a decrease in the incidence of tumors with a Gleason score of 6 or below. The researchers presented their findings at the 24th Annual European Association of Urology Congress in Stockholm.

The overall incidence of advanced-stage and high-grade tumors was not affected, but the researchers pointed out that the low number of cases impeded these analyses. Alpha-blocker use did not significantly reduce prostate cancer risk. The researchers also observed no difference in median PSA by medication-use status among men later diagnosed with prostate cancer.

The current study shows that among systematically screened men participating in a randomized screening trial, the incidence of low-grade, early-stage tumors is decreased in men using finasteride for symptomatic BPH, the investigators wrote. “This suggests that the protective effect of finasteride can be expected also in men with average risk of prostate cancer,” they wrote.

One of the investigators, Teemu Murtola, MD, of the University of Tampere School of Public Health in Finland, said he believes that the evidence of finasteride’s protective effect against prostate cancer is sufficient for physicians to discuss with patients the drug’s use as a way to prevent prostate cancer, especially if the patient has some risk factors, such as positive family history or elevated PSA but negative biopsy findings. 

“As our study shows,” Dr. Murtola told Renal & Urology News, “the protective effect can be expected also in men with benign prostatic hyperplasia. This information could be used to improve patients’ motivation to use finasteride as treatment of BPH. However, the possible increased risk of high-grade cancers indicates [the need for] close patient follow-up during finasteride therapy.”

Eric A. Klein, MD, of the Cleveland Clinic in Ohio, whose research interests include the chemoprevention of prostate cancer, noted that “although the effect of finasteride on cancer risk was not the primary end point of this trial, the results confirm the effects of this agent in reducing the risk of prostate cancer [as were demonstrated] in the Prostate Cancer Prevention Trial.” That trial showed that men who took finasteride experienced a 25% reduced risk of prostate cancer.

Dr. Klein, who is chairman of the clinic’s Glickman Urological & Kidney Institute, noted that the Finnish study findings “add to the growing body of evidence that use of finasteride is beneficial and safe for this indication.”

Recently, the American Society of Clinical Oncology and the American Urological Association issued a guideline regarding the use of 5α-reductase inhibitors for prostate cancer chemoprevention.

According to the guideline, asymptomatic men with a PSA level of 3 ng/mL or less who are screened regularly with PSA tests or are anticipating having annual PSA screening for early detection of prostate cancer may benefit from a discussion of both the advantages of taking 5α-reductase inhibitors for seven years to prevent prostate cancer and the potential risks, such as the possibility of high-grade prostate cancer.