Single Agent Gemcitabine Chemotherapy in Dogs with Spontaneously Occurring Lymphoma

Background:Gemcitabine has been shown to be effective as a single agent in a variety of tumors including nonHodgkin's lymphoma. Its use in veterinary medicine has been limited and to date this drug has not been used as a first‐line therapy in dogs with lymphoma. Hypothesis:Gemcitabine as a single agent may be efficacious in dogs presented for the first time with lymphoma. Animals:Twenty‐four dogs with spontaneously occurring lymphoma. Methods:All dogs were clinically staged and given gemcitabine at 400 mg/m 2 over a 30‐minute intravenous infusion weekly for 3 weeks and then given 1 week off treatment before starting a second cycle. Results:A single dose of gemcitabine lowered both neutrophil count (decrease in mean neutrophil count from 10,640 cells/μL to 3,140 cells/μL) and platelet count (decrease in mean platelet count from 201,290 cells/μL to 139,190 cells/μL) 7 days after administration. Consequently gemcitabine dosage was reduced at the second treatment in 8 of 21 dogs or a dose delay of 1–7 days and a reduction of dosage was used in 7 of 21 dogs. Seven dogs completed the assigned 4‐week cycle. Two of these dogs had progressive disease and 5 had stable disease. No objective responses were seen in dogs treated with a second cycle of gemcitabine. Conclusions and Clinical Importance: Gemcitabine administration as a single agent resulted in hematologic toxicity and did not reduce lymphoma burden. If gemcitabine is to be used in veterinary medicine, additional prospective pharmacologic studies should be done to determine the appropriate dosage, regimen, and schedule of use before it can be recommended for use in the treatment of dogs with lymphoma as a single agent.