Objective: To determine whether cisplatin administered at a dosage of 60 mg/m2 of body surface area, IV, every 21 days, would induce remission of transitional cell carcinoma of the urinary bladder in dogs.
Design: Retrospective analysis of medical records.
Animals: 18 dogs with histologically confirmed transitional cell carcinoma of the urinary bladder.
Procedure: Clinical staging was performed by means of physical examination, contrast cystography or ultrasonography, and thoracic radiography prior to and 42 days after the initiation of cisplatin treatment. Dogs with clinical signs of tumor progression were reevaluated earlier than 42 days in some instances. Complete remission (CR) was defined as complete resolution of measurable tumor. Partial remission (PR) was defined as a > or = 50% reduction in tumor volume without development of new tumors. Stable disease was defined as < 50% change in tumor volume at 42 days without development of new lesions. Progressive disease (PD) was defined as > or = 50% increase in tumor volume or development of new tumors at any time. Dogs were reevaluated at 42-day intervals until they had a CR, developed PD, or developed unacceptable adverse effects.
Results: Three dogs had a PR, 4 had stable disease, and 9 had PD. Tumor response could not be assessed in 2 dogs: 1 dog developed grand mal seizures 3 hours after the first dose of cisplatin was given and was euthanatized; the other dog continued to have clinical signs of urinary tract obstruction and was euthanatized 8 days after the first dose of cisplatin. Four dogs developed renal azotemia that was suspected to be secondary to cisplatin nephrotoxicity.
Clinical implications: The cisplatin dosage was higher than that reported in studies of dogs with transitional cell carcinoma of the bladder. Even with this higher dosage, none of the dogs had a CR, and only 3 of 18 had a PR. A more effective, less toxic treatment for transitional cell carcinoma in dogs is needed.