Regional chemotherapy using continuous intravesical infusion doxorubicin for the treatment of muscle invasive transitional cell bladder carcinoma in a rat model.

Previously established animal models of invasive transitional cell bladder carcinoma and continuous infusion intravesical drug delivery were combined to evaluate the urothelial toxicity and antineoplastic efficacy of continuous intravesical infusion doxorubicin (DOX). Dose-response toxicity experiments studied histologic changes in the rat urinary bladder following urothelial exposure to three different urinary levels of DOX, as a function of the duration of drug infusion. Systemic and local drug absorption, as measured by DOX levels in serum, bladder, retroperitoneal lymph nodes, and liver, was measured at intervals during drug administration. In vitro chemosensitivity assays were used to determine tumor sensitivity to DOX. Treatment studies evaluated the impact of 14-day continuous infusion DOX beginning seven days following tumor implantation. No histologically discernable changes in the normal urothelium were noted in bladders of animals receiving continuous intravesicle DOX at mean urinary concentrations of 0.05 micrograms./ml. (n = 5), 0.56 micrograms./ml. (n = 10), and 5.69 micrograms./ml. (n = 10) for periods of up to 14 days. Serum drug concentrations demonstrated a non-significant upward trend following the start of therapy. Significant increases in tissue DOX levels were noted in the bladder and retroperitoneal lymph nodes on chemotherapy days 7 and 14. Mean tissue DOX concentrations in both the bladder and lymph nodes were greater than the IC50 observed in the in vitro sensitivity assay. DOX-treated tumor-bearing animals (n = 17) had a mean tumor volume (+/- standard deviation) of 0.65 gm. +/- 0.52 gm. compared to an average tumor volume of 1.20 gm. +/- 0.66 gm. in the control group (n = 18) (p = 0.0112). Continuous infusion intraluminal chemotherapy demonstrated a clear cytoreductive effect with minimal local toxicity in this model. Drug tissue levels were observed in regional lymphatic drainage fields as well as the bladder wall. Further study to evaluate this approach as a bladder-sparing alternative to muscle invasive disease is warranted.