Tolerability of Gemcitabine and Carboplatin Doublet Therapy in Cats with Carcinomas

Background: This study was performed to determine the toxicity of gemcitabine-carboplatin doublet therapy in cats with carcinomas. Hypothesis: Gemcitabine and carboplatin are safe in tumor-bearing cats. Animals: Twenty cats with spontaneously occurring carcinomas. Methods: A cohort of 6 cats received gemcitabine (2 mg/kg IV) on days 1, 8, and 15 and carboplatin (10 mg/kg IV) immediately after gemcitabine on day 1 of a 21-day cycle. A 2nd cohort of 14 cats received carboplatin 4 hours after gemcitabine on day 1 and gemcitabine on day 8 but not day 15. The cycles were repeated every 21 days. Results: Cats in the 1st cohort received a median of 3.75 cycles per animal (range, 1–6). Two cats (33.3%) developed grade 3 or 4 neutropenia, 1 (16.7%) grade 4 thrombocytopenia, and 1 (16.7%) grade 3 gastrointestinal toxicity. Gemcitabine dose reductions and treatment delays occurred in 1 and 4 cats, respectively. Cats in the 2nd cohort received a median of 2 cycles per animal (range, 0.5–10). Two cats (14.3%) had grade 3 or 4 neutropenia and 1 (7.1%) had grade 3 and 4 gastrointestinal toxicity. One cat required gemcitabine dose reduction and 6 had treatment delays. In the 2nd cohort, of 11 cats with measurable tumors, there was 1 complete response (pancreatic carcinoma) and 1 partial response (squamous cell carcinoma, receiving concurrent nonsteroidal anti-inflammatory drugs). Conclusions and Clinical Importance: Gemcitabine-carboplatin combination appears moderately well tolerated in tumor-bearing cats. Minimal patient benefit suggests that alternative schedules or combinations of gemcitabine with other agents should be explored.