Hepatic tumor radioembolization in a rat model using radioactive rhenium (Re-186/Re-188) glass microspheres

Purpose: The aim of this study was to fully characterize newly developed ra dioactive rhenium glass microspheres in vivo by determining their biodistri bution, stability, antitumor effect, and toxicity after hepatic arterial in jection in a syngeneic rat hepatoma model, The dose response of the tumors to increasing amounts of radioactive Re-186 and Re-188 microspheres was als o determined. Methods and Materials: Rhenium glass microspheres were made radioactive by neutron activation and then injected into the hepatic artery of Sprague-Daw ley rats containing 1-week-old Novikoff hepatomas, The biodistribution of t he radioactivity and tumor growth were determined 1 h and 14 days after inj ection. Results: Examination of the biodistribution indicated a time-dependent, up to 7-fold increase in Novikoff hepatoma uptake as compared to healthy liver tissue uptake. After 14 days, the average T:L ratio was 1.97, Tumor growth in the rats receiving radioactive microspheres was significantly lower tha n in the group receiving nonradioactive microspheres (142% vs. 4824%,p = 0. 048), Immediately after injection, 0.065% of the injected radioactivity was measured in the thyroid; it decreased to background levels within 24 h, Conclusion: Radioactive rhenium microspheres are effective in diminishing t umor growth without altering hepatic enzyme levels. The microspheres are sa fe with respect to their radiation dose to healthy tissue and radiation rel ease in vivo and can be directly imaged in the body with a gamma camera. Fu rthermore, rhenium microspheres have an advantage over pure beta-emitting m icrospheres in terms of preparation and neutron-activation time. In sum, th is novel radiopharmaceutical may provide an innovative and cost-effective a pproach for the treatment of nonresectable liver cancer, (C) 1999 Elsevier Science Inc.