Found your whole response interesting and helpful. Maybe radiopharmaceuticals for BCR, hopefully without all the adt pre treatment.

I had narrowed my research down to Proton or the MRIdian from viewray. I am 69. PSA was 10.2. Did Decipher and spaceoar. Healthy tissue exposure was key to my decision. Proton had a precise beam but used 4-6 mm margins with fused images and positioning and movement a real issue. I went with Viewray and finished my 5 treatments in February. 2 mm margins, combo radiation MRI unit, auto turn off and dynamic plan adjustment, if needed. Google the Mirage study. I had minimal side effects with urination.

BMC publishing did an article in May of 2020 discussing a built in mri into a proton therapy machine, which does not exist in the marketplace. Had that existed, with some of the extras, I would have chosen it.