Research Highlights

Ian Thompson
Ian Thompson, MD

One of the discoveries from the Prostate Cancer Prevention Trial (PCPT) was that taking finasteride (5a-reductase inhibitor), resulted in a 25% reduction in cancer risk, but when the prostate cancer occurred despite finasteride intake, it was associated with an increased risk of being diagnosed with high-grade disease. In order to identify the impact, if any, on survival, we analyzed rates of survival among all study participants and among those with prostate cancer. For this report, we collected data on the incidence of prostate cancer among PCPT participants for an additional year after the first study report was published in 2003 and searched the Social Security Death Index to identify survival status through October 31, 2011, which provided us with up to 18 years of follow-up data.

Among the 18,880 eligible men who were randomized and followed in the PCPT, prostate cancer was diagnosed in 989 of 9423 (10.5%) in the finasteride group and 1412 of 9457 (14.9%) in the placebo group. Among the study participants who were diagnosed with prostate cancer, 333 (3.5%) in the finasteride group and 286 (3.0%) in the placebo group had a high-grade cancer (meaning a Gleason score of 7 to 10). The 15-year survival rate was 78.0% for the finasteride group and 78.2% for the placebo group with a total of 5034 deaths reported, 2538 and 2496, respectively. The unadjusted hazard ratio for death in the finasteride group was 1.02 (95% CI, 0.97 to 1.08; P=0.46). When men were classified according to cancer grade, the 10-year survival rates were 83.0% for the finasteride group and 80.9% for the placebo group among those with low-grade prostate cancer and 73.0% and 73.6%, respectively, for those with high-grade prostate cancer. This analysis of study data indicates a significant reduction of the risk of prostate cancer in the finasteride group compared to the placebo group by reducing the risk of getting prostate cancer by about one third. Although a high-grade prostate cancer was more common in the finasteride group than in the placebo group, after 18 years of following study participants, there was no significant difference between the two groups in either the rate of survival after a diagnosis of prostate cancer or the rate of overall survival.

Concisely, data from 18 years of follow-up showed that the use of finasteride over a period of 7 years in a general population of men with a median age at study entry of 63.2 years reduced the risk of prostate cancer but did not significantly affect mortality. This reduction in risk was entirely due to a relative reduction of 43% in the risk of low-grade cancer among men receiving finasteride, as compared with placebo. Although the prevention of these tumors did not appear to reduce overall mortality, increased diagnosis of low-grade prostate cancer is a problematic by-product of PSA testing, in that treatment adds little, if any, benefit and in that all forms of therapy cause considerable burden to the patient and to society.

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