DUTASTERIDE MAY SUPPRESS ONLY TEMPORARILY PROSTATE CANCER DEVELOPMENT 

NEW YORK (Reuters Health) Jan 29 - While the risk of prostate cancer appears to be reduced in men taking dutasteride, there is some indication that cancer may emerge once the drug is discontinued.

That finding comes from a two-year follow-up of men who had participated in the four-year REDUCE trial, which compared prostate cancer rates in men receiving the 5-alpha-reductase inhibitor (5ARI) dutasteride versus those given placebo.

The REDUCE trial included men at increased risk of prostate cancer due to older age (50-75 years) and increased PSA levels (2.5-10 ng/mL) with a prior negative prostate biopsy. Compared to placebo, dutasteride reduced the relative risk of biopsy-detectable prostate cancer during the study by 22.8%.

The main aim of the current REDUCE Follow-Up Study was to assess the occurrence of prostate cancer in the two years following the conclusion of the REDUCE study.

"This study shows that with 2 additional years of follow-up after REDUCE study there were few new cancers diagnosed among patients in either the dutasteride or placebo group. Importantly, none of these cancers were high grade cancers (Gleason Score 8-10)," principal investigator Dr. Robert L. Grubb commented in an email to Reuters Health.

However, he added, "Because of the small number of cancers it is difficult to draw many strong conclusions."

A total of 2,751 of the original participants were enrolled in the follow-up study. During that time, no drugs were provided and all biopsies were performed for cause.

Very few prostate cancers were detected during follow-up, but there were more in the former dutasteride group. Specifically, there were 14 cases among former dutasteride recipients compared to 7 among the former placebo group, Dr. Grubb, at Washington University School of Medicine in St. Louis, Missouri, and colleagues report.

"A possible reason for this difference is that any prostate cancer that may have been suppressed by dutasteride during REDUCE was no longer being suppressed for those subjects who did not continue 5ARI therapy," the authors, most of whom are employees of GlaxoSmithKline, suggest in their report in the March issue of the Journal of Urology.

This is supported by the fact that, among the former dutasteride-treated patients, prostate cancer rates during follow-up were 0.9% in those who continued to take a 5ARI compared to 1.3% for those who did not continue on a 5ARI, the authors point out -- although the confidence intervals for both estimates are wide.

Still, as Dr. Grubb mentioned, no high-grade prostate cancers were detected during the follow-up study in either the former dutasteride or placebo groups.

"The possible induction of high-grade tumors is an area of concern with the use of 5-alpha reductase inhibitors," he explained. "This study shows that with 2 years further follow-up beyond the original REDUCE trial there were no Gleason 8-10 tumors diagnosed."

Furthermore, he added, "Significant adverse events were rare among both the dutasteride and placebo groups, including cardiac events."

Dr. Grubb and colleagues caution that, while the study provides real-world observational data, it has limitations. No statistical tests were conducted, because the subjects were not randomized in the follow-up study, and most data were based on subject recollection.

GlaxoSmithKline paid for editorial support in preparing the report.

SOURCE: http://bit.ly/T3WOCb

J Urol 2013;189:871-877.