Localization of avidin in superficial bladder cancer: a potentially new approach for radionuclide therapy

OBJECTIVE: To verify whether native avidin, made radioactive through the binding with technetium-99m labeled biotin (99mTc-biotin), selectively accumulated in superficial tumor tissues following intravesical administration. METHODOLOGY: A total of fifteen patients with transitional cell bladder cancer were instilled intravesically with radiolabeled avidin. Cold biopsies were obtained from macroscopically normal and tumor tissues before transurethral resection (TUR) and the radioactivity in the samples was measured. RESULTS: Increased accumulation of radiolabeled avidin was observed in tumor tissue compared to normal bladder tissue and in some cases, remarkably high quotients of uptake (q) in tumor versus normal tissues were determined (86 and 44). The three patients instilled with a deglycosylated avidin at neutral pI, who served as a control, showed no significant uptake in either tumor or normal urothelium and no difference in relative uptake (q=1.0). CONCLUSION: This pilot study indicated that intravesical administration of radiolabeled avidin resulted in a preferential accumulation in tumor tissue compared to normal urothelium. The instillation of radiolabeled avidin warrant further investigations in order to explore the possibility to treat superficial bladder neoplasms locally by replacing 99mTc with high energy beta emitting radionuclides associated with biotin.