Where to begin?
As for the study in question:
They found many more incidences of cancer than would normally be expected in the general population because of the rigorous testing (blood tests as well as prostate boipsies) that was performed on all patients. rostate cancer is probably one of the most survivable cancers and several studies have asserted that those treated for prostate cancer had an overall worse survival rate than those who were untreated. In this case, finasteride reduced the overall incidence of tumors, but increased the liklihood of developing and aggressive tumor (very bad). The tumors that finasteride prevented were small tumors that probably would not have been of consequence in everyday life.
Now, for those who take anabolic steroids, finasteride can be a life saver. If you take steroids that are converted by 5 alpha reductase into more potent metabolites (testosterone to DHT is the biggie) then finasteride could help prevent serious prostate problems in the future. Finasteride will lower libido, but this has nothing to do with gains, period. DHT is deactivated in skeletal muscle by the enzyme 3 alpha hydroxysteroid dehyrogenase (forming androstanedione), so the loss of DHT should have no negatie impact on skeletal muscle hypertrophy (if you have very high DHT levels, then one could exceed the capacity of 3 alpha hydroxysteroid dehydrogenase and in this case, one would notice a decrease in gains -- but, your prostate at these levels would probably be the size of a grapefruit). Even thoug hi stated that prostate cancer is very survivable and has a lower incidence than was found in this study, high levels of androgens will increase the liklihood of BPH, prostate cancer and a negative outcome if cancer develops.