A study in February’s Journal of Vascular and Interventional Radiology found that patients undergoing liver cancer treatment with Theraspheres?, radioactive microspheres containing Yittrium-90, can tolerate a 150 Gy single dose or 268 Gy repeated dose without risk of radiation-induced liver disease.
This paper looked at the pretreatment factors and radiation dose levels that affected toxicity that could be used to determine which patients can benefit from Theraspheres.
Many patients with liver cancer have impaired liver function due to underlying cirrhosis and/or the tumors themselves. Thus, they are at increased risk for liver toxicity from any liver cancer treatment. In the United States, approximately 50-60 percent of patients with primary liver cancer, or hepatocellular carcinoma, die of tumor progression and 40-50 percent die from advancing cirrhosis and subsequent liver failure.
Although surgical removal of liver tumors offers the best chance for a cure, it is not possible for more than three-fourths of primary liver cancer patients and 90 percent of patients with secondary liver cancer. For these patients, this new nonsurgical treatment offers them an option that can give them more time. “Because systemic therapy has the potential to induce toxic effects without an associated benefit, reliance on the use of local and regional treatments like radioembolization is expanding in the United States,” stated study author Riad Salem, MD, MBA, interventional radiologist, Northwestern University.
The study showed that the risk of toxicity from the treatment appeared to be related to the patient’s pre-treatment total bilirubin level and the mean liver radiation dose. Since bilirubin levels can be used as an indicator of liver function and predict a possible predisposition for liver toxicity, they can help interventional radiologists select patients for this treatment. In this study, liver toxicity occurred in 42 percent of the patients; however, most of the toxicities resolved after treatment and those that did not were attributed to tumor progression or advancing cirrhosis. In the patients studied, radiation-induced liver disease was not observed, and no patient died of liver failure attributed to treatment.
Radioembolization incorporates the radioactive isotope Yttrium-90 into the embolic spheres to deliver radiation directly to the tumor. Each sphere is about the size of five red blood cells in width. An interventional radiologist injects these beads through a catheter from the femoral artery in the groin to the liver artery supplying the tumor. The beads become lodged within the tumor vessels where they exert their local radiation that causes cell death. This technique allows for a higher, local dose of radiation to be used, without subjecting healthy tissue in the body to the radiation. The Yttrium-90 radiates from within and, since it is administered in the hepatic artery, can be viewed as “internal” radiation. This treatment is approved by the Food and Drug Administration for the treatment of unresectable hepatocellular carcinoma, or as a bridge to transplantation.