Some great comments to a vexing question.

I was told I am not a candidate for proton therapy due to the volume and location of cancer cells in my prostate and pelvic region. So instead of Eligard plus proton as the initial course of treatment, it is Eligard plus Erleada for several months in hope they will reduce the volume and edges sufficiently for proton to be viable.

If hormone therapy does not kill the cancerous kills how is the volume reduced? By ablation from the shear on their surface from the circulating blood flow? Chunks of dormant cancer cells get "ripped off" from the tumor? So the volume of the tumors are reduced but the now circulating cancerous cells either cannot adhere elsewhere or it they do it is not a big deal since they are not growing/growing very slowly?

Med science sure ain't physics.