I can well imagine that producing antiprotons is expensive. I wonder what kind of antiproton fluxes are involved for this kind of therapy
I also wonder how much of the destructive effect is due to radiation, e.g. gamma rays, produced by the particle annihilation. Offhand I imagine that the higher the radiation production by annihilation, the less localized the destruction would be.
It's exciting when the world of high energy physics comes into contact with the world of medicine.