It seems that the seminal vesicle involvement is the really bad news. These are glands attached to the prostate which are removed as part of the radical prostatectomy. Prognosis-wise it means that there is now a high chance that the cancer will (or maybe has already) spread elsewhere. I guess maybe the fact that it is established in this non-prostate tissue means that it has the ability to spread? According to one prostate calculator, http://www.prostatecalculator.org/, I now have a 39% chance of remaining cancer free (according to PSA tests) for the next seven years. So the odds are now dipping below even that I am cured.
My doctor is recommending that we do nothing now and test PSA in a month's time. If it is undetectable then just keep watching, but if the PSA is there then to consider enrolling in an experimental treatment where hormone therapy (testosterone suppression) is combined with chemotherapy. I will have to do some more research about this. I know that radiation and/or hormone therapy might be an option at this point also. Time to check the second opinions again I think.