Radioembolization with Yttrium-90 microspheres: review of an emerging treatment for liver tumors.

Understanding the effect of radiation on tissue, the principles of dosimetry and fractionation have led to the acceptance and adoption of radiation as a standard treatment option for cancer. Delivered in staged and scheduled aliquots, radiation will break nucleic strands and cause cellular death. In general, radiation therapies are delivered using external techniques (external beam and intensity-modulated therapy). One of the limitations of such external techniques is that of nontarget radiation. That is, despite best efforts to collimate and reflect radiation beams to a small target, nontarget radiation and a dose to areas outside the tumor remains a distinct possibility. With the advent of radioembolization using Yttrium-90 microspheres (90Y), the radiation source is delivered optimally through a novel mechanism: directly into the blood vessel providing flow to the tumor. This revolutionary approach capitalizes on the basic principles of tumor hypervascularity, concentrating radiation within that tumor, while at the same time minimizing the risks of nontarget radiation. This review elaborates on this technology.