Tiny Radioactive Spheres Increase Survival and Reduce Liver Metastases When Combined with Chemotherapy
Tiny radioactive spheres can reduce the size of liver metastases in patients and significantly increase survival, according to results of this phase III trial that tested the effect of adding a single dose of the spheres to chemotherapy delivered into the hepatic artery, which feeds the liver.
The study enrolled 71 patients whose colorectal cancer had spread to the liver and for whom surgically removing these liver metastases was not an option. The patients were randomized to receive either chemotherapy alone or chemotherapy plus the radioactive spheres. The treatments were injected into the hepatic artery, because liver tumors derive 80 percent of their blood supply from this artery, whereas the normal liver receives only 20 percent of its blood from the artery. The micro-encapsulated spheres, called "SIR-Spheres," contain high doses of yttrium-90 which can be dissolved by the liver.
The study, led by Dr. Guy van Hazel from Sir Charles Gairdner Hospital, in Perth, Australia, found that 14 percent of patients who used chemotherapy plus the spheres had a total response compared to 9 percent in the chemotherapy group. In addition, 56 percent of patients who were treated with both therapies had a partial response compared to 47 percent in patients who just received chemotherapy. The combination therapy also significantly delayed progression of cancer, van Hazel reports. After two years, 42 percent of patients who used the spheres were alive, compared to 26 percent of patients treated with chemotherapy alone.
Dr. Van Hazel noted that the strategy of this approach is to deliver radioactive substance directly to the tumor. This is novel, as nonselective external beam radiation to the liver can result in excessive toxicity. This therapy delayed progression of liver metastases, however, median survival was the same. Dr. Van Hazel cautioned that this study is a subset analysis and was therefore not designed to answer this specific question. Further studies should be done to better clarify the full efficacy of this treatment.