Vincristine-induced adverse events related to body weight in dogs treated for lymphoma.

Abstract

Traditional dosing of chemotherapy drugs based on body surface area may overdose small dogs, leading to an increased frequency of adverse events (AEs). Evaluate the frequency of hematologic and gastrointestinal AEs in dogs with newly diagnosed lymphoma treated with vincristine weighing ≤15 kg in comparison to dogs weighing >15 kg. We hypothesized that dogs weighing ≤15 kg would experience a higher frequency of AEs. One hundred and thirty-eight dogs with newly diagnosed lymphoma were treated with vincristine. A multicenter retrospective study reviewing hematologic data and medical record information. Complete blood counts were performed no more than 24 hours before vincristine administration and then between 4 and 8 days post-administration. Data were evaluated using logistic regression or ordinal logistic regression. Thirty-eight dogs weighing ≤15 kg and 100 dogs weighing >15 kg were included. The median vincristine dose for both groups was 0.6 mg/m2. Seventeen (12.3%) instances of neutropenia occurred with no significant difference in overall frequency or grade between groups. Thirty initially asymptomatic substage A dogs (29.4%) experienced gastrointestinal AEs. Because of the widespread use of gastrointestinal supportive care medications, statistical comparison between groups could not be performed. Seven instances of hospitalization occurred (5.0%) and the risk of hospitalization did not differ significantly between groups (P = .37). Vincristine dosed at ≤0.6 mg/m2 does not increase the risk of hematologic AEs in dogs weighing ≤15 kg.