Yes- Fred Huchinson is top notch. UWSeattle was where many of the techniques used today in brachytherapy were developed. Swedish Medical also has an excellent reputation. I know Robert Meier there has done some excellent work with SBRT - certainly worth a visit while you're in Seattle.
Yes, your prostate is too big for seeds right now. However, with your GS 4+3, they might recommmend you start with a short course of hormone therapy. That will shrink your prostate considerably and it will radiosensitize the nasty cancer cells for the upcoming radiation. I think they would recommend a combination of external beam and seeds. In a big clinical trial, they found that that combination (HT+external beam+brachy) had the highest cure rates in intermediate risk men like yourself. In that study, with 9 years of follow-up, biochemical progression-free survival (meaning there was no increase in PSA to indicate recurrence) was an astounding 94%.
/pcnrv.blogspot.com/2017/03/brachy-boost-gold-standard-for.htmlThere are two types of radiotherapy, SBRT and high-dose-rate brachytherapy that have no prostate size restrictions, and do not have to be combined with external beam radiation or hormone therapy. Robert Meier can tell you about
SBRT. There must be someone in Seattle who does HDR-brachy, but I don't know who that is.
He is right that AS is a really bad option unless you have limited life expectancy for some other reason.
Staging (whether the cancer is still confined to the prostate) is difficult pre-treatment. Even the best MRIs only detect existing extraprostatic extension about
half the time - not much better than a coin toss. If he felt a big lump, he might want to check it on an MRI. Absent that, you have to go by nomograms and Partin tables, which can only give you probabilities for people like you, but not what is specifically going on in you. This is why the cure rates are so high with the brachy boost combination therapy - it treats cancer both inside and outside of the prostate capsule.