I will be frank about this: the ONLY reason to have surgery (which I had for G4+3 unfavorable) is if your type of cancer has a higher degree of recurrence - that’s it! If it does, you can have salvage radiation (which I just completed) to try yo kill it again.
The factors you should concern yourself with are: presence of cribriform/IDC, high Gleason score - intermediate unfavorable or aggressive (8-10), and a high Decipher Score - which is an ABSOLUTE MUST before you can make a decision. If it is considered low you are in a good place. You don’t mention having this crucial test.
Other than those factors I can think of no reason why a 73 yr old man should subject himself to life altering surgery. Robotic surgery is NOT as precise and exact as it is claimed to be - better than open surgery but still PLENTY of side effects.
You have 20% cancer in your cores - that’s nothing compared to mine - like 90%!
SBRT/Cyberknife/MRIdian are all 5 treatment events that are probably better than surgery at this point since those head-to-head comparisons are very old. Proton/photon not such a game changer in outcomes IMO but proton supposedly has less SE’s so if you can get proton, why not?
It’s always your decision but you must educate yourself, sift thru this forum using the search button for specific questions you may have. I am giving you MY input based on my own experience and that of others on this board. I don’t speak for everyone but I think many members will nod in the affirmative when they read this post. Best,
Phil