A second opinion on the biopsy slides is a great idea. You can ask for an MRI for staging, but you should know that they are not all that good - no better, in fact, at predicting EPE for intermediate risk guys like yourself than a nomogram like this one:
/www.mskcc.org/nomograms/prostate/pre-opYour age isn't any reason to decide for one therapy or another. At a younger age like yours, you are likely to have fewer side effects of treatments compared to older guys, and better recovery is expected. That's true for both surgery or radiation. Given that surgery or radiation is about
equally curative for cases like yours, you have to decide based on other factors, like side effects and the importance of a pathology report.
If confirmed by Epstein, good treatment options for you include surgery, external beam with a low dose rate (seeds) brachytherapy boost, SBRT, or high dose rate brachytherapy. I hope you will seek out and talk to specialists in all of those before deciding. Short term hormone therapy for men with GS 4+3 may make it more effective for some kinds of radiation therapy (like IMRT or LDR brachytherapy), but has no known benefit for other kinds of radiation therapy (like SBRT or HDR brachytherapy).
As for salvage options, salvage is effective in about
half the cases. That is true whether it is salvage radiation after a first line prostatectomy, or focal brachytherapy or focal ablation salvage after first line radiation treatment.
If you tell us where you are, we may have suggestions for specialists in your area.