Tumor localization and systemic absorption of intravesical instillation of radio-iodinated iododeoxyuridine in patients with bladder cancer

Purpose: We evaluated tumor uptake and systemic distribution of intravesically instilled iododeoxyuridine (IUdR) in patients with superficial bladder cancer. Materials and Methods: We performed 24 intravesical instillation studies in 11 patients with a mean age of 71 years. Radio- iodinated IUdR was administered through a Foley catheter. Gamma camera imaging was done after instillation and after 5 to 7 bladder irrigations. Tumor uptake was estimated by region of interest analysis. Bladder biopsy samples and surgical tumor specimens were tested for acid insoluble (deoxyribonucleic acid incorporated) radioactivity. Blood samples were obtained and analyzed for systemic absorption. Results: Imaging was positive in all patients with bladder cancer. Average tumor uptake plus or minus standard deviation was 0.185 ± 0.120% of the instilled dose. Preferential uptake of IUdR in the tumor was observed in all 6 patients undergoing tissue analysis. The tumor-to-normal bladder ratio ranged from 3.2 to 74,000 (median 202). Systemic absorption of IUdR was minimal. Blood sample analysis performed after intravesical instillation in all 11 cases revealed an average uptake of 3.2 x 10^-5% instilled dose per ml. (range 0.69 x 10^-5 to 6.7 x 10^-5) in the systemic circulation. Instillation within 24 hours after transurethral bladder tumor resection in 5 cases resulted in a higher but not dangerous average systemic uptake of 7.3 x 10^-4% instilled dose per ml. (range 1.3 x 10^-5 to 2.6 x 10^-3). Instillation 1 to 4 weeks after transurethral surgery in 8 cases resulted in no increased systemic absorption with an average blood level of 3.4 ± 1.8 x 10^-5% instilled dose per ml. There was no detectable distribution of radioactivity into other organs, including the thyroid. We noted no evidence of systemic toxicity in the study. Conclusions: Intravesical instillation of radio-iodinated IUdR achieves selective localization in the bladder tumor with minimal uptake by the normal bladder and minimal systemic absorption. The use of intravesical IUdR therapy for bladder cancer appears to be promising and requires further study.