Let us know what part of the world you are in and some member nearby may have some helpful information about treatment facilities and experienced physicians.
It is unfortunate that no annual PSA check-up was done since before age 50 - at least!
As you start this fight from where you are, keep posting and many with similar medical circumstances can give you a heads up on options your physicains might not review with you.
My experience is that once a physician is nervous about a situation / apparent oversight, they become so careful about what they say and do that it hinders things a little.
Be clear about this: YOU NEED A SECOND OPINION! Just because you are from a small town does not preclude this. Any good physician (and almost all insurance) will welcome this.
Examine all of your options. If radiation is recommended, at least investigate Proton Therapy. as an alternative.
May God's Love be with you, always - in the Son!