[188Re]rhenium sulfide suspension:: A potential radiopharmaceutical for tumor treatment following intra-tumor injection

Intralesional therapy has been shown to be an effective treatment for tumors. In this study, the suitability of [Re-188]rhenium sulfide suspension for tumor treatment following intra-tumor injection was evaluated. The [Re-188]rhenium sulfide suspension was radiolabeled with Re-188 with a radiochemical yield of more than 96%. In vitro stability studies revealed that more than 99% of the Re-188 remained in sulfide form over a 3-day period. After ultrasonication for 5 or 10 min, the main particle size was 1-5 mu m. Two [Re-188]rhenium sulfide suspensions ultrasonicated for 5 and 10 min, respectively, were injected into separate group of tumor-bearing mice that were killed after specified times to compare the retention of Re-188 in tumors and the leakage to different organs by periods and organs removed to gamma counting. The mean retention percentages of Re-188 in tumors injected with suspension ultrasonicated for 5 (or 10) min were as follows: 1 h, 90.5 +/- 7.7% (83.1 +/- 13.7%); 24 h, 92.2 +/- 8.6% (83.9 +/- 9.8%); 48 h, 88.3 +/- 10.9% (80.2 +/- 3.8%); and 72 h, 91.5 +/- 7.6% (78.8 +/- 3.0%). Tumor-inhibiting ratio was 96.5%. These results demonstrated that [Re-188]rhenium sulfide suspension is an effective radiopharmaceutical for tumor treatment by intralesional therapy. (C) 1999 Elsevier Science Inc. All rights reserved.