Neutropenia associated with vincristine and L-asparaginase induction chemotherapy for canine lymphoma

Vincristine (VCR) and L-asparaginase (L-ASP) are commonly used to treat canine lymphoma. As single agents, these drugs are not myelosuppressive. However, in combination, VCR and L-ASP cause severe neutropenia in some dogs. It has been recommended that L-ASP be administered 12-24 hours after VCR to minimize toxicity. The purpose of this retrospective study was to determine the prevalence of neutropenia after VCR/L-ASP induction therapy for canine lymphoma and to evaluate risk factors for myelosuppression, especially the interval between VCR and L-ASP administration. Medical records of 147 dogs were reviewed. L-ASP was given 0 (n = 50), 6 (n = 23), 18 (n = 20), or 24 (n = 54) hours after VCR. Forty percent of the dogs were neutropenic 7 days after VCR/L-ASP, and 18% had neutrophil counts of <1,000 cells/microL. The median neutrophil count was 3,712 cells/microL (range 0-30,968 cells/microL). No correlation was found between administration interval and day 7 neutrophil count (P = .84) or development of gastrointestinal signs, including vomiting (P = .80), diarrhea (P = .52), and decreased appetite (P = .30). No significant predictors of neutropenia were identified. Higher clinical stage and substage b were associated with decreased appetite after treatment (P = .04 and .01, respectively). Sixteen percent of the dogs were hospitalized. This study demonstrates that VCR/L-ASP induction for canine lymphoma may result in neutropenia but that separation of VCR and L-ASP administration may not be necessary to avoid toxicity.