Evaluating the potential of ¹⁸⁸re-ecd/lipiodol as a therapeutic radiopharmaceutical by intratumoral injection for hepatoma treatment

Background/Objectives: Intratumoral injection of a radiopharmaceutical is a potential modality to treat liver tumors. Rhenium-188 (¹⁸⁸Re) was used to chelate with ethyl cysteinate dimer (ECD) in lipiodol solution to form ¹⁸⁸Re-ECD/lipiodol, which was then evaluated for its therapeutic potential in a rodent hepatoma model. Materials and Methods: Male Sprague-Dawley rats were implanted with N1-S1 hepatoma cells orthotopically and randomly divided into two groups. Group 1 (=29) and group 2 (=10) received ¹⁸⁸Re-ECD/lipiodol (30.4 > ±21.8MBq/0.1mL) and 0.1 mL of normal saline by intratumoral injection, respectively. Three rats in group 1 were imaged by micro-single-photon emission computed tomography/computed tomography scan to evaluate the biodistribution pattern. All rats were monitored for change of tumor size and survival rate after 2 months. Results: The in vitro stability test showed that ¹⁸⁸Re-ECD was well-retained in the lipiodol phase for 48 hours. The biodistribution image revealed that radioactivity was retained well in hepatomas 24 hours postinjection. Long-term studies demonstrated that rats treated with ¹⁸⁸Re-ECD/Lipiodol had smaller tumor volumes and a better survival rate, compared to the control group. At the end of observation, the survival rates in groups 1 and 2 were 62% and 20%, respectively (p<0.05). Conclusions: ¹⁸⁸Re-ECD/lipiodol via direct intratumoral injection shows potential for treating hepatoma and warrants further clinical trials.