Embolization particles

The present invention relates to an embolization particle comprising a microparticle coated with a plurality of nanoparticles, which nanoparticles comprise a metal oxide doped with one or more rare earth elements, wherein the metal oxide is titanium dioxide, zinc oxide or cerium dioxide. An embolization particle of the invention for use in the treatment of cancer in combination with X-ray radiation or proton beam radiation, or use in embolization, is also described. The invention also relates to a process for producing an embolization particle comprising a microparticle coated with a plurality of nanoparticles, which nanoparticles comprise a metal oxide doped with one or more rare earth elements, wherein the metal oxide is titanium dioxide, zinc oxide or cerium dioxide, which process comprises : (i) providing a microparticle; (ii) contacting the microparticle with a plurality of the nanoparticles; and (iii) heating the microparticle and the nanoparticles to form the embolization particle.