Web265 said it all - everything in the prostate bed/pelvic area gets irradiated with higher doses going to the bed and the nodes.
My treatment at Sloan was called IGRT - Intensity Guided RT - which is a bit more descriptive in that a cone beam Xray is taken at the beginning of each session (as with Web265) and the beams are ‘guided’ around bladder, bowel and rectum.
But they are all photonic; I’ve had previous discussions on the forum about the efficacy about proton radiation for SRT and why you would even use it, but many hospital websites say that they CAN use proton for this.
I am sure the physics involved is way above my pay grade!
Best,
Phil