...

Here's a citation to a brief story by a guy whose graft was
successful - or at least that's what the story says.

 http://www.phoenix5.org/stories/firstpers/persNeuralGraft.html

The surgeon was the famous urologist Dr. Peter Scardino, who
would be a top choice for surgery even without the graft.  I
think he's in Chicago.

I found it by Googling.  A search on the following terms will get
hits:

    neural graft prostatectomy

Another option is radiation.  The outcomes regarding potency are
said to be about the same as for surgery.  However if the surgeon
has already ruled out nerve sparing surgery, impotence is
guaranteed.  Radiation has at least a chance of sparing potency.
The size of that chance depends on your friend's current age and
potency (older and less potent men have worse outcomes) and,
probably, on the skill of the radiation oncologist.  One rule of
thumb I was given is that radiation has about a 50% chance of
sparing potency.  I think that, with radiation, it's also less of
an all or nothing thing.

However I wouldn't chose radiation if I thought surgery had a
better chance of a cure.  The key thing is to beat the cancer.
Sex is only possible while you're alive!  For myself, I chose
radiation and I'm happy with the outcome.  But it's hard to say
which is better, and also hard to say which cases might benefit
most from which treatment.  The decision on surgery vs. radiation
is a very controversial one with strong partisans on each side.
Anecdotal stories of success or failure are a poor guide to which
treatment to choose.

Assuming your friend chooses surgery, he should know that the
nerves that are cut in a prostatectomy are the ones that enable
erections.  They're not the ones involved in sexual pleasure or
orgasm.  With a willing partner, sex is still possible and can
still be very satisfying even without potency.  There are also
other treatments like prostaglandin injections that can often
produce an erection in a man who otherwise couldn't have one.

Best of luck to him on beating the cancer and on coming out of it
in good shape.

    Alan

I doubt that even the medical industry knows that answer.  I lost both
nerves and had a useable erection 2½ years later.  I was then assaulted with
radiation and then with hormones, then double-down hormones and damn if I
didn't have an erection twice in the last year.

Compared to that, how could anyone say that neural grafts are successful or
if the body just did its job?

Thanks for all the replies. I didn't include a lot of details because I only
knew that his doctor, oncologist, urologist told him that his cancer was too
close to the margins to save the nerves, and I possibly thought the graft
might be worth a try.
Thanks again