INTRATUMORAL INJECTION OF RE-188 MICROSPHERES INTO AN ANIMAL-MODEL OFHEPATOMA

Intratumoral injection of Y-90 microspheres is a potential alternative in the treatment of primary liver tumor. However, complicated prepara tion and lack of a gamma ray for imaging are the disadvantages of Y-90 , In this study, we used Re-188, a generator-produced radioisotope wit h 155-keV gamma ray emission, to label microspheres, After intratumora l injection of Re-188 microspheres into rats with hepatoma, biodistrib utions and survival times were analyzed. Methods: Twelve male rats wit h hepatoma were killed at 1, 24 and 48 hr (4 rats at each time point) after intratumoral injection of similar to 7.4 MBq 188Re microspheres, Samples of various organs were obtained and used to calculate the tis sue concentrations. In addition, 30 male rats bearing hepatoma were di vided into two groups (15 rats in each group) to evaluate survival tim e. Group 1 received intratumoral injection of 37 MBq Re-188 microspher es, whereas Group 2 served as the control group and received an intrat umoral injection of 0.1 mi normal saline only. Survival time was calcu lated from the day of injection to 2 mo after treatment. Results: Radi oactivity in the tumor was very high throughout. Biological half-time was 170.8 hr. Radioactivity in the lung was 1.78% injected dose (ID)/g at 1 hr but declined rapidly over time. The concentration in the urin e was similar to 6.14% ID/ml after the first hour and rapidly declined thereafter. The concentrations of radioactivity in other organs, such as normal liver, muscle, spleen, bone, testis and whole blood, were q uite low throughout the study. Twelve of 15 (80%) of rats survived ove r 60 days after intratumoral injection of Re-188 microspheres, whereas only 4 of 15 (26.7%) survived more than 60 days after injection of no rmal saline only. The difference between the groups was significant (p < 0.05). Conclusion: Rhenium-188 offers cost-effectiveness, on-site a vailability, short half-life, energetic beta particle, emission of gam ma photons for imaging, easy preparation, easy clinical administration and apparent lack of radiation leakage from the treated tumor. Direct intratumoral injection of Re-188 microspheres is extremely attractive as a clinical therapeutic alternative in hepatoma patients.