Intratumoral injection of rhenium-188 microspheres into an animal model of hepatoma.

ABSTRACT

UNLABELLED Intratumoral injection of 90Y microspheres is a potential alternative in the treatment of primary liver tumor. However, complicated preparation and lack of a gamma ray for imaging are the disadvantages of 90Y. In this study, we used 188Re, a generator-produced radioisotope with 155-keV gamma ray emission, to label microspheres. After intratumoral injection of 188Re microspheres into rats with hepatoma, biodistributions and survival times were analyzed. METHODS: Twelve male rats with hepatoma were killed at 1, 24 and 48 hr (4 rats at each time point) after intratumoral injection of approximately 7.4 MBq 188Re microspheres. Samples of various organs were obtained and used to calculate the tissue concentrations. In addition, 30 male rats bearing hepatoma were divided into two groups (15 rats in each group) to evaluate survival time. Group 1 received intratumoral injection of 37 MBq 188Re microspheres, whereas Group 2 served as the control group and received an intratumoral injection of 0.1 ml normal saline only. Survival time was calculated from the day of injection to 2 mo after treatment. RESULTS: Radioactivity in the tumor was very high throughout. Biological half-time was 170.8 hr. Radioactivity in the lung was 1.78% injected dose (i.d.)/g at 1 hr but declined rapidly over time. The concentration in the urine was approximately 6.14% i.d./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 quite low throughout the study. Twelve of 15 (80%) of rats survived over 60 days after intratumoral injection of 188Re microspheres, whereas only 4 of 15 (26.7%) survived more than 60 days after injection of normal saline only. The difference between the groups was significant (p < 0.05). CONCLUSION: Rhenium-188 offers cost-effectiveness, on-site availability, short half-life, energetic beta particle, emission of gamma photons for imaging, easy preparation, easy clinical administration and apparent lack of radiation leakage from the treated tumor. Direct intratumoral injection of 188Re microspheres is extremely attractive as a clinical therapeutic alternative in hepatoma patients.