Eagle, if you were pT3b, it means cancer was found in at least one seminal vesicle. If so, I would say the chances are very good that you weren't G6 (3+3). For example:
One of the 3,290 Gleason score 6 cases (0.03%) showed seminal vesicle invasion compared to 93 of the 4,202 (2.2%) of Gleason score 3 + 4 = 7 (p <0.0001).
Conclusions: It is not rare for pure Gleason score 6 prostate cancer to locally extend out of the prostate 3.9% focally and 2.4% nonfocally. In extremely rare cases Gleason score 6 can be associated with seminal vesicle invasion and yet not lymph node metastases. Our overall findings support the argument for continuing to use the term cancer for these tumors." (From a 2018 study
(Bladder-neck invasion should be now be graded the same as extraprostatic extension, pT3a
If you were G7 (3+4) with SVI+ as your only adverse finding, I believe current standard of care would not be adjuvant RT, but rather to hold off until/unless your PSA goes up. Keep in mind that since the seminal vesicles are removed along with the prostate, it is possible that all you PCa was eliminated at surgery.
I would have my RP tissue and slides sent to Dr. J. Epstein at JHU in your case for a definitive answer regarding your pathology. If you are then still concerned, you could ask your docs about
having a Decipher test done on your RP tissue to determine your risk (low, intermediate, high) for developing mets within 5 years.