Jim:
Thank you for a concise presentation of your case. Your pathology reports post-operative are critical. First, the stage description is p (pathological, or post op) T2b (Tumor involves half of one lobe, or more, of the gland) Nx (lymph nodes not assessed [likely not removed]) M(Metastases in distant locations not identified). Thus pT2bNxM(x?).
Neoplastic tissue is another word for cancerous tissue. The part of your prostate that was not cancer demonstrated several areas of near cancerous definition (intraepithelial neoplasia and hyperplasia). This is of less interest for the current discussion
Your post surgical psa should be zero, or as close to zero as the assay allows. Yours is not, though it is declining. A critical issue is the margin identified at the Apex. This means that there was cancerous growth at the edge of the resected (cut) tissue. This may well be the source of your psa, though it is not certain that it means you still have cancer tissue. Where was this margin? Was it outside of the prostate itself? If so this means that the surgeon took tissue from just outside the prostate, as he should, but was not able to remove all cancer cells that had spread from this area of the gland. On the other hand, if the surgeon cut just inside the edge of the prostate, he may have left behind some original prostate cells which continue to produce psa, though perhaps not cancerous. This would be unclear without more information from the Pathology report.
Best case, your remaining prostate cells produce small amounts of psa and you can monitor it for many years without further treatment. Or, if the remaining cells were cancerous, cut from their blood supply they wither and the psa continues down to zero, or nearly so.
Next case, psa dribbles around at a low level for a while with no particular direction or a slow decline, and further treatment decisions are delayed until a clear trend is identified.
Last case, there is a clear call from all evidence that surgical failure has occurred and treatment decisions are discussed.
One very important factor you mention is Gleason score, or the rating of the aggressiveness of the cells. It would be an important piece of information in the Path report about the ratio of G3 to G4. Any G4 is a higher risk issue and must be considered in decisions. If you had 3+4 90%/10% (less troubling) this is different than 55/45.
If radiation is determined to be the next step, sooner rather than later is the usual practice. Your positive margin is certainly highly suspicious as the culprit for this continued psa.There are side effects to radiation, usually of the urinary and sexual kind. For a man your age, even if radiation does not cure, then if it delays progression this can be meaningful. SWOG 8794 clinical trial (Google it) may provide you with interesting reading.
I am not a medical professional. My advice is worth what you pay for it. In addition to your surgeon, an oncologist and radiologist may well be consulted. The work of your surgeon is done. Further treatments, if any, will be outside his specialty.
Let us know how it goes.