Background: The dosage of carboplatin in cats has been reported anecdotally and experimentally in non-tumor-bearing cats, but the dosage for carboplatin treatment in tumor-bearing cats has yet to be defined in a prospective clinical trial.
Purpose: To determine the maximally tolerated dose (MTD) and dose-limiting toxicosis (DLT) of carboplatin in tumor-bearing cats.
Cats: Fifty-nine cats with measurable solid tumors.
Methods: The starting dose of carboplatin was 160 mg/m2 of body surface area IV. Doses were increased by 20 mg/m2 in cohorts of 3–14 cats until the MTD was reached.
Results: The 59 cats entered into this multi-institutional phase I study received 1 or more doses of carboplatin at various dosages and were evaluated for toxicity, response to treatment, or both. The MTD was 240 mg/m2 and neutropenia was the DLT. For the 1st cycle of treatment in 44 cats evaluated for neutropenia, 6 episodes of grade 3 or greater neutropenia occurred on days 7 (n=1), 14 (n=4), and 21 (n=1). There was no evidence of drug-induced nephrotoxicosis or pulmonary edema. Preliminary evidence of antitumor activity was observed in 7 of 59 (11.9%; 95% CI, 5.6–22.8%) cats evaluated for response to treatment. There was 1 complete response (cutaneous hemangiosarcoma) and 6 partial responses (4 injection site sarcomas, 1 oral squamous cell carcinoma, 1 lymphoma). Responses were of short duration (median, 42 days; range, 7–168 days).
Conclusions and Clinical Importance: The dose of carboplatin recommended to treat tumor-bearing cats is 240 mg/m2 IV every 3–4 weeks.