Fractionated intravesical radioimmunotherapy with 213Bi-anti-EGFR-MAb is effective without toxic side-effects in a nude mouse model of advanced human bladder carcinoma

Gold standard in therapy of superficial, non-muscle invasive urothelial tumors is transurethral resection followed by intravesical instillation therapies. However, relapse is commonly observed and therefore new therapeutic approaches are needed. Application of 213Bi-immunoconjugates targeting EGFR had shown promising results in early tumor stages. The aim of this study was the evaluation of fractionated application of 213Bi-anti-EGFR-MAb in advanced tumor stages in a nude mouse model. Luciferase-transfected EJ28 human bladder carcinoma cells were instilled intravesically into nude mice following electrocautery. Tumor development was monitored via bioluminescence imaging. One day after tumor detection mice were treated intravesically either two times with 0.93 MBq or three times with 0.46 MBq of 213Bi-anti-EGFR-MAb. Therapeutic efficacy was evaluated via overall survival and toxicity towards normal urothelium by histopathological analysis. Mice without treatment and those treated with the native anti-EGFR-MAb showed mean survivals of 65.4 and 57.6 d, respectively. After fractionated treatment with 0.93 MBq of 213Bi-anti-EGFR-MAb animals reached a mean survival of 141.5 d and 33% of the animals survived at least 268 d. Fractionated treatment with 0.46 MBq 213Bi-anti-EGFR-MAb resulted in a mean survival of 131.8 d and 30% of the animals survived longer than 300 d. Significant differences were only observed between the control groups and the group treated twice with 0.93 MBq of 213Bi-anti-EGFR-MAb. No toxic side-effects on the normal urothelium were observed even after treatment with 3.7 MBq of 213Bi-anti-EGFR-MAb. The study demonstrates that the fractionated intravesical radioimmunotherapy with 213Bi-anti-EGFR-MAb is a promising approach in advanced bladder carcinoma.JRC.E.5-Nuclear chemistr