Studies showing that men taking Proscar (finasteride) had a statistically significant increase in high-grade tumors lessened interest in using Proscar to prevent prostate cancer and as a treatment for enlarged prostate.
A recent new study challenged this finding and suggested that the increased detection of high-grade prostate cancers in those men taking finasteride maybe be related to the drug’s ability to improve the PSA test’s performance and not to its induction of high-grade disease.
This interpretation is only one possible interpretation of the data - and the interpretation that, in my opinion, a drug company would like to get to the public.
The other interpretation – and, in my opinion, more likely the accurate one - is that proscar can cause regression of BPH and low-grade prostate cancer for a while, but it cannot handle high grade prostate cancer.
So, in patients taking Proscar, the PSA goes down as the BPH and any low-grade cancer regresses. However, if there is high-grade cancer present, it goes on growing.
Because high-grade cancer frequently produces less PSA on a cell-for-cell basis, the PSA rises less with high-grade cancer as the cancer grows. Therefore, by the time the PSA rises high enough to arouse suspicion, the prostate contains a substantial amount of high-grade cancer that is more aggressive and less susceptible to treatment than the mix that was present before the Proscar.
These men have not really benefitted from taking the Proscar. It has only served to delay the diagnosis of nasty cancers until they have grown large enough to produce enough PSA to make up for that lost from benign tissue and/or low-grade cancer.