recent publication looked at the longterm effects of finasteride (see N Engl J Med 2013;369:603-10, DOI: 10.1056/NEJMoa1215932). the 15-year survival rates were no different between groups (78.0% with finasteride and 78.2% with placebo). the 10-yr survival rates for men with low-grade prostate cancer was 83% with finasteride and 80.9% with placebo; for high-grade prostate cancer: 73.0% vs 73.6%
so, pretty clear that not so useful to try to prevent prostate cancer with finasteride (to me, would have been surprising to be beneficial, since the high grade tumors are more dysplastic and less likely to respond to normal endocrine stimulation which is blocked by finasteride). but, at least this study shows that finasteride is pretty benign (i have been hesitant to use it for BPH because of the initial findings, but will use more now if indicated clinically).
geoff