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The Pharmaceutical Journal
Vol 271 No 7256 p4
5 July 2003

Related websites
New England Journal of Medicine abstract (more)
Journal of the National Cancer Institute abstract (more)

Finasteride reduces risk of prostate cancer but doubts remain over its use

Finasteride seems to prevent or delay the appearance of prostate cancer. However, doubts over whether such cancers are clinically significant and concerns about finasteride's effect on the growth of high-grade cancers lessen the attractiveness of the drug as a chemoprotective agent.

Dr Ian Thompson, University of Texas Health Science Centre, San Antonio, and colleagues, randomly assigned 18,882 men considered to have a low risk of prostate cancer to 5mg finasteride per day or placebo. The men were monitored annually and followed up for seven years.

Prostate cancer was detected less frequently in the men treated with finasteride (18.4 per cent versus 24.4 per cent), who had a reduction in relative risk of 24.8 per cent (95 per cent confidence interval, 18.6 to 30.6 per cent, P<0.001). However, high-grade tumours were more common among these men (37.0 per cent versus 22.2 per cent of tumours). The incidence of adverse effects on sexual function was higher with finasteride, although this was offset by beneficial effects on urinary function.

"For a man considering using this medication, the greater absolute reduction in the risk of prostate cancer must be weighed against the smaller absolute increase in the risk of high-grade disease," say the researchers (New England Journal of Medicine 2003;349;213).

In an accompanying editorial (ibid, p295), Dr Peter Scardino, department of urology, Memorial Sloan-Kettering Cancer Centre, New York, says: "On balance, finasteride does not seem to be an attractive agent for the chemoprotection of prostate cancer." He adds that although it reduced the cumulative incidence of cancer, the reduction was relative to a high incidence of cancers in the control group. Furthermore, the malignant potential of the cancers is not known. "We ... have no evidence that any benefit would be worth the risk associated with treatment," he says.

Men taking finasteride for the relief of urinary symptoms should probably not be advised to stop taking the drug but should be carefully monitored for the development of cancer, he adds.

Zinc and prostate cancer Men who take high doses of zinc supplements could be at increased risk of prostate cancer, say researchers from the National Cancer Institute in Bethesda, Maryland. They looked at the association between supplement use and prostate cancer risk in 46,974 men and found that, compared with non-users, men who consumed more than 100mg of zinc supplements per day had more than double the risk of developing the disease (relative risk 2.29, 95 per cent confidence interval 1.06 to 4.95, P=0.003 for trend). Intake of up to 100mg of zinc supplements per day was not associated with an increased risk of prostate cancer (Journal of the National Cancer Institute 2003;95:1004).