My experience so far is at least not inconsistent with that.  I started
taking 200 micrograms of selenium daily in the middle 90s on the
recommendation of my primary care physician.  Later I began to worry
about the possible side effects of too much selenium, so I stopped for a
while.   The problem is that it is easy to overdose on selenium since it
is also a normal part of a healthy diet.  But when my PSA started
increasing, I went back to using it.  My PSA actually decreased from a
high of 4.5 to 3.8, but that may have been normal statistical variation.
 Also, although my biopsy showed a Gleason 7=3+4, the post surgical
biopsy showed no change in the Gleason and the cancer was confined to
the prostate.  Of course, it is impossible to know if the selenium had
any effect in slowing down the development of my cancer.

More recently, I've looked at the details of the study currently
underway comparing selenium + vitamin E with a placebo, and I concluded
that 200 micrograms daily is safe.   But since the upper limit is
something like 400 micrograms daily, one has to be careful about
multivitamins containing selenium and the rest of one's diet.

I plan to continue with selenium + Vitamin E in the hopes that it will
lower the risk of recurrence, unless of course future studies show no
effect for prostate cancer or other cancers.