Perspectives

1.5 Perspectives

Improvements in radiolabelling techniques have resulted in increasingly stable
microspheres with a leakage of less than 0.1% of the activity. Three major
radiolabeled microsphere materials, glass, resin-based and polymer-based are now
available for therapy or are being tested in animals. The only commercially available
glass-type 90Y microspheres are very stable and have a proven reputation in the
treatment of primary or metastatic hepatic cancer, but their high density is a serious
drawback. Consequently, less dense particles have been developed in the form of resin
and polymeric spheres. Resin-based spheres also have a high chemical stability and,
with half the density of glass, they provide good prospects for the treatment of liver
cancer. Resin particles are currently being investigated in patients, and these particles
show results comparable to glass. Polymeric microspheres like poly(L-lactic acid)
spheres have a near plasma density and additional advantages such as biocompatibility
and biodegradability. A polymeric sphere appears to be the best particle for this kind
of therapy, although with the drawback of low resistance to irradiation in a nuclear
reactor. Recent studies have demonstrated that polymeric microspheres can be
prepared with sufficient amounts of activity for therapeutic application. These
microspheres are therefore one of the future materials for use in the battle with liver
cancer. Other oncological applications such as the treatment of head-and-neck cancer,
bone metastases and ovarian cancer are in the pipeline. Internal radionuclide therapy
is likely to play a substantial role in the control of hepatic and other types of cancer in
the future.