Ceramic microspheres for in situ radiotherapy of cancer

Radiotherapy is one of the effective treatments of cancers. External irradiation, however, often causes damages to healthy tissues. It has been reported that chemically durable 17Y2O3–19Al2O3–64SiO2 (mol%) glass microspheres 20–30 μm in diameter are useful for in situ irradiation of cancers. This glass microsphere is already clinically used for treatment of liver cancer in USA, Canada and China. The number of yttrium ions present in this glass microsphere is, however, not very large. On the other hand, P-31 can be activated to ß-emitter P-32 with a little longer half-life of 14.3 days by neutron bombardment. Therefore, it is expected that chemically durable microspheres containing a large amount of yttrium or phosphorus 20–30 μm in diameter are useful for in situ radiotherapy, when they were previously activated to ß-emitter by neutron bombardment. In the present study, Y2O3 and YPO4 microspheres were prepared by high-frequency induction thermal plasma melting method, and their structure, chemical durability and distribution in organs of rabbit were examined. The Y2O3 and YPO4 microspheres not only contained a large amount of yttrium or phosphorus but also showed high chemical durability. The Y2O3 microspheres were uniformly distributed only in their target organ and did not distribute in other organs. Therefore, they are believed to be useful for in situ radiotherapy of cancer.